What processing does to a spice
Between the harvest and the jar a spice is dried, cured, smoked, milled, treated to reduce its microbial load, packed and stored, and each step changes its colour, its aroma, its pungency or its keeping. These are the measurements, one study at a time, with the conditions each was made under. Choose a step and a spice. The steps themselves are described in how spices are produced and processed, and what a cook does to a spice in what cooking does to a spice.
Showing all 145 findings.
Toasting and dry roasting · Converts Gingerol, Shogaol
Fresh ginger from one Korean farm held 6200 mg of 6-gingerol per kilogram of dry weight and only 29 mg of 6-shogaol. Dry heat in a convection oven moved gingerol towards shogaol, faster as the temperature rose from 100 to 130 °C. After 360 min at 130 °C the 6-gingerol in sliced fresh ginger had fallen from 6243 to 2877 mg/kg while 6-shogaol had risen to about 1350 mg/kg; the paper gives 1161 mg/kg for the same sample in a later passage.
Conditions: in air · 100, 110, 120 and 130 °C in a convection oven · 10 to 360 min · Fresh ginger in 5 mm slices and freeze-dried ginger powder, from one farm
What it means in practice:Heat alone, without any drying step beforehand, shifts ginger from gingerol towards shogaol, but in this study the shift took hours at oven temperatures above the boiling point of water. A few minutes in a pan is a far smaller treatment than anything measured here.
What this does not show: One farm, one harvest and a laboratory oven, with heating times of up to six hours. The paper reports two different shogaol figures for the same sample. It measured the pungent compounds only, not taste, and did not measure zingerone.
Measured on the spice
Toasting and dry roasting · Converts Gingerol, Shogaol
Under the same dry heat, dried ginger powder converted more of its gingerol than sliced fresh ginger did. After 360 min at 130 °C the powder went from 6288 to 2265 mg of 6-gingerol per kilogram and reached 1611 mg/kg of 6-shogaol, significantly more than the slices. The authors attribute the difference to the energy the fresh slices spend evaporating their water before they can heat up.
Conditions: in air · 130 °C in a convection oven · 360 min · Freeze-dried ginger powder compared with 5 mm slices of fresh ginger
What this does not show: The powder was freeze-dried in the laboratory so that it began with almost no shogaol; commercially dried ginger already contains some. The explanation offered for the difference was proposed by the authors, not tested.
Measured on the spice
Toasting and dry roasting · Decreases Curcumin
Thermogravimetric analysis of curcumin showed decomposition in two stages, and led the authors to conclude that where curcumin is used as a food colouring the processing temperature should not exceed 190 °C.
Conditions: in air · Heated progressively in a thermogravimetric instrument · Pure curcumin as used for food colouring
What this does not show: Read in the abstract only. The pure pigment heated dry in an instrument, with loss of mass as the measure; chemical change that does not release volatile products would not be seen. It is not a measurement of turmeric in a pan or an oven.
Measured on the pure compound
Toasting and dry roasting · Forms Canolol (2,6-dimethoxy-4-vinylphenol), Sinapic acid
Roasting mustard seed forms canolol, 2,6-dimethoxy-4-vinylphenol, a compound made from the seed’s sinapic acid; it was isolated from roasted mustard seed oil and its identity confirmed by synthesis. About half of the canolol formed in the roasted seed passed into the oil pressed from it. Under similar roasting, the mustards produced less than a third as much as rapeseed.
Conditions: in air · Seed roasted before oil extraction; Brassica juncea, B. nigra and Sinapis alba compared with rapeseed
What this does not show: Read in the abstract only, which gives no roasting temperature or time. The study concerns oil pressed from roasted seed, as made in Nepal, and reports the compound’s effect on the oil’s resistance to oxidation, not on flavour.
Measured on the spice
Toasting and dry roasting · Decreases total carotenoids, β-carotene, esterified xanthophylls, colour
Ground paprika held at 80 °C for 8 h lost extractable colour and carotenoids, and the loss depended on where the paprika came from. The Peruvian paprika fell from 198.1 to 161.9 ASTA units, a significant change; the Chinese paprika fell from 196.2 to 172.9, which was not significant. The section on colour puts the carotenoid loss at about 50 per cent in the Peruvian samples and about 26 per cent in the Chinese. The authors attribute the difference to the higher share of esterified carotenoids in the Chinese paprika, and observe that ASTA units did not register the carotenoid difference between the two origins until the loss reached about half.
Conditions: in air · 80 °C · 8 h · Ground sweet paprika from Peru and from China, as an accelerated oxidation test
What it means in practice:ASTA colour is a coarse instrument: in this test a quarter of the carotenoids could disappear without the ASTA value changing significantly.
What this does not show: The abstract gives the carotenoid losses as 70 per cent and 30 per cent where the body of the paper gives about 50 per cent and 26 per cent; both are reported in the paper and neither is corrected there. An oven test at 80 °C is not shelf storage.
Measured on the spice
Frying and blooming in fat · Converts Curcumin, Deketene curcumin
Curcumin heated to the point of pyrolysis, alone or in coconut fat or olive oil, gave a number of more hydrophilic isomers and decomposition products. One of them was identified by NMR as deketene curcumin, a compound previously known only as a synthetic derivative.
Conditions: in oil or fat · Curcumin pyrolysed with and without coconut fat or olive oil; products followed by HPLC
What this does not show: Read in the abstract only, which gives neither the temperature nor the yield. It establishes that curcumin is chemically altered by strong heating in fat, not how much survives ordinary frying.
Measured on the pure compound
Frying and blooming in fat · Converts Capsaicin, Vanillin, Methylnonenoic acid, Methylnonenamide, 9-Octadecenamide, N-Vanillyl-9-octadecenamide
Capsaicin decomposed by heat gives vanillin, methylnonenoic acid and methylnonenamide. Heated together with oleic acid, a fatty acid common in cooking oils, it also forms two products of reaction with the fat: 9-octadecenamide and N-vanillyl-9-octadecenamide.
Conditions: in oil or fat · High temperature; not stated in the published summary · Pure capsaicin alone and mixed with oleic acid; products identified by GC-MS
What this does not show: Read in the abstract only, which states neither the temperature nor how much of the capsaicin decomposed. Pure compound with a single fatty acid, not chilli in a cooking oil.
Measured on the pure compound
Frying and blooming in fat · Decreases Capsanthin, colour
Paprika oleoresins lost pigment at every temperature tested, and more quickly the warmer they were held, but the loss was not even across the pigments. Below 60 °C the yellow carotenoid fraction was destroyed faster than the red; above 60 °C the order reversed and the red fraction became the less stable. Heating above that temperature therefore shifts the remaining colour towards yellow.
Conditions: in oil or fat · Four temperatures, either side of 60 °C · Four paprika oleoresins
What this does not show: Read in the abstract only, which gives no rates or times. An oleoresin, the extracted pigment in its own oil, not the ground spice.
Measured on the spice
Frying and blooming in fat · Converts Hydroxy-α-sanshool, Hydroxy-β-sanshool, Hydroxy-ε-sanshool, Dihydroxy oxidation products, pungency
Hydroxy-α-sanshool, the principal tingling compound of Sichuan pepper, degraded markedly on heating in oil, and the more so the higher the temperature. Heat converted it into its isomers hydroxy-β-sanshool and hydroxy-ε-sanshool, and oxidised it to dihydroxy compounds.
Conditions: in oil or fat · Supercritical carbon dioxide extract of Zanthoxylum diluted in soybean oil
What it means in practice:The tingle of Sichuan pepper is the part of it that hot oil damages, which is in keeping with the practice of infusing it gently or adding it late.
What this does not show: Read in the abstract only, which gives no temperatures, times or rates. A commercial extract in oil. Whether the isomers formed still tingle is not addressed there.
Measured on the spice
Simmering and boiling · Converts Gingerol, Shogaol
In water, [6]-gingerol loses a molecule of water to give [6]-shogaol, and the reaction runs both ways: shogaol takes water back up to re-form gingerol until the two reach a balance. The rate depended on acidity, with gingerol most stable at pH 4. At 100 °C and pH 1 the reaction was relatively fast and reached equilibrium within 2 h. Shogaol was the major degradation product.
Conditions: in water · 37 to 100 °C · pH 1, 4 and 7 · Pure [6]-gingerol in aqueous solution, followed by HPLC
What this does not show: Read in the abstract only. A solution of the pure compound, studied for pharmaceutical purposes; pH 1 is far more acid than any food. The abstract gives no rate constants and does not report zingerone.
Measured on the pure compound
Steaming · Converts Gingerol, Shogaol
Moist heat converted gingerol to shogaol far more effectively than dry heat at the same temperature. After 360 min in an autoclave the 6-gingerol in sliced fresh ginger had fallen from 6258 mg/kg of dry weight to 4436 mg/kg at 100 °C, 2840 at 110 °C, 746 at 120 °C and 571 at 130 °C. The highest 6-shogaol content in the study, 2991 mg/kg, came from 360 min of moist heat at 120 °C, roughly twice what dry heat produced in the same slices.
Conditions: in steam · 100, 110, 120 and 130 °C in an autoclave · 10 to 360 min · Sliced fresh ginger under pressurised moist heat
What it means in practice:At 100 °C, the temperature of a simmering pot, six hours of moist heat still left about seven tenths of the 6-gingerol in place. The large conversions in this study belong to pressurised heat above the boiling point.
What this does not show: An autoclave, not a pot: the ginger was heated in pressurised steam, not simmered in liquid, so nothing could leach out. One farm and one harvest. Zingerone was not measured.
Measured on the spice
Steaming · Depends on conditions Shogaol
Shogaol did not accumulate without limit. Under moist heat at 130 °C, 6-shogaol rose to a maximum of 2890 mg/kg of dry weight at 240 min and then fell with further heating; under dry heat at 130 °C the powder likewise peaked at 240 min and declined slightly afterwards. At 120 °C, by contrast, shogaol was still rising at the end of the 360 min tested.
Conditions: in steam · 130 °C · Up to 360 min; the peak came at 240 min
What this does not show: The study did not identify what the shogaol became once it began to fall. The times involved are far longer than cooking times.
Measured on the spice
Steaming · Depends on conditions β-Caryophyllene, Oxygenated monoterpenes, α-Gurjunene, Linalool, volatile oil
Before treatment, β-caryophyllene made up 82 per cent of the headspace volatiles of black pepper and 59 per cent of those of white pepper. After 5 min of moist heat at 105 °C it had fallen almost to trace level in both, the share of sesquiterpene hydrocarbons as a class had dropped, and oxygenated compounds had risen; linalool in black pepper went from 0.02 to about 1.5 per cent of the profile.
Conditions: in steam · 105 °C in an autoclave · 5 min · Peppercorns wrapped in foil; headspace SPME GC-MS, relative percentages
What this does not show: Relative percentages of a headspace profile from one lot, with wide variation between replicates, so a compound can rise in share simply because another has fallen. A sterilising treatment, not cooking. The authors read the change as an improvement in aroma, but no sensory test was run.
Measured on the spice
Steaming · Depends on conditions Curcumin, colour
A mobile steam vessel built to cook turmeric before drying brought the cooking time to 10 min, against 15 min in a parboiling drum and 25 min by the open steaming that the authors describe as farmers’ practice. The design aim was to retain as much curcumin as possible while shortening the cook. Rhizomes cooked in the vessel gave colour values of L 53.74, a 58.46 and b 18.16.
Conditions: in steam · 10 min in the new vessel; 15 min in a parboiling drum; 25 min by open steaming · A wheeled steam vessel holding 100 kg of rhizomes
What this does not show: Read in the abstract only, which states the aim of retaining curcumin but gives no curcumin figures and no colour values for the other two methods. An equipment paper from one group.
Measured on the spice
Extracting in alcohol · Extracts Vanillin
Of six solvents tried on cured vanilla pods, the polar ones, which include ethanol, extracted the most vanillin by both methods tested. Extraction was slow: at 95 °C with 66.67 mL of solvent per gram of pod, Soxhlet extraction released around 180 ppm of vanillin in 8 h, and raising the temperature from 90 to 100 °C increased the extraction by 30 per cent.
Conditions: in alcohol · Soxhlet extraction at 90 to 100 °C; ultrasound-assisted extraction at ambient temperature · 8 h by Soxhlet; 1 h with ultrasound · Cured pods; ethanol, methanol, acetonitrile, acetone, chloroform and hexane compared
What this does not show: Read in the abstract only, which does not say which solvent gave the figures quoted. A process-engineering comparison of extraction equipment; vanillin alone was measured, and it is only one part of the aroma of a vanilla extract.
Measured on the spice
Crushing and cutting · Depends on conditions shikimic acid, particle size, volatile oil
Of three ways of breaking down star anise and cinnamon, steam explosion left the lowest levels of both volatile and non-volatile compounds. Ordinary crushing and a vacuum collision process that reduced particles to a far finer size gave flavour profiles similar to each other and distinctly different from the steam-exploded material, and the main active components did not differ significantly between those two.
Conditions: Physical crushing, vacuum nano-collision and steam explosion compared; cinnamon was treated alongside
What this does not show: Read in the abstract only, which does not say which species of cinnamon was used and gives no volatile contents. The particle size it reports for the finest treatment is implausibly small and is not repeated here.
Measured on the spice
Grinding · Decreases Monoterpenes, Sesquiterpenes, volatile oil
Black pepper ground at ambient temperature lost about 50 per cent of its volatile oil compared with the same pepper ground cryogenically, and the loss fell on every monoterpene measured. In sensory assessment the cryogenically ground pepper was distinctly stronger in the top notes that read as freshness and marginally stronger in its base notes.
Conditions: Ambient grinding against cryogenic grinding at product temperatures down to −20 °C · Pilot-scale pin mill at several feed rates
What it means in practice:The heat of milling is itself a cause of aroma loss, before any storage begins, and it takes the lightest compounds first. The figure belongs to an industrial pin mill; a hand mill or mortar heats the spice far less and was not tested.
What this does not show: Read in the abstract only. Industrial milling equipment; the loss is stated relative to cryogenic grinding, not to the whole berry, and one lot of pepper was used.
Measured on the spice
Grinding · Increases Allyl isothiocyanate
Ground mustard seed meal released allyl isothiocyanate when it took up moisture from humid air alone, without being wetted. Both the rate and the amount released rose with relative humidity and with temperature between 5 and 35 °C, and the rate could be altered through the particle size and the fat content of the powder. Between 2 and 17 mg were released per gram of powder within 24 h.
Conditions: in air · 5, 20 and 35 °C · Release followed over 24 h · Meal ground to powders of 5 to 300 µm · Defatted and partly defatted meal in sealed jars at 85 or 100 per cent relative humidity
What it means in practice:Water is a reagent in making mustard’s heat, not just a carrier for it, and even damp air supplies enough to start the reaction in ground seed. A mustard powder kept dry is keeping its pungency unspent.
What this does not show: Read in the abstract only. A packaging study on defatted meal, aimed at antimicrobial use, and the abstract does not say in which direction particle size or fat content moved the rate.
Measured on the spice
Grinding · Increases Eugenol, Cyperene, Phenethyl isovalerate, volatile oil, yield
Clove buds ground before being boiled in water gave up twice as much essential oil as whole buds: 14.3 per cent of their weight against 7.14 per cent after six hours of distillation. The composition changed as well. Eugenol was the major compound in both oils, but it made up 87.4 per cent of the oil from whole buds and 68.7 per cent of the oil from ground ones, in which cyperene rose from 7.2 to 20.5 per cent.
Conditions: in water · Boiling water at atmospheric pressure · 6 h of hydrodistillation · 50 g of clove buds, whole or ground in an electric grinder, in 500 mL of water
What it means in practice:A whole clove releases its oil slowly and incompletely even to hours of boiling, which fits its use whole in long-cooked dishes; ground clove gives up much more, and a broader mixture of compounds.
What this does not show: One lot of cloves and one grinder, with composition as relative peak areas. Distillation removes the oil continuously, so the yields are not the amounts that would be found in a cooking liquid.
Measured on the spice
Grinding · Depends on conditions total flavonoids, particle size, colour, antioxidant capacity, volatile oil
Coriander ground in a hammer mill came out finer than coriander ground in a pin mill, and its browning index was higher: 57.7 to 70.7 across the moistures tested, against 56.2 to 60.8 from the pin mill. The authors put both down to the screen of the hammer mill, which holds the seed in the grinding zone until it is fine enough. Average particle size ran from 0.34 to 0.46 mm and rose significantly as seed moisture rose from 6.4 to 13.6 per cent. Total flavonoid content and radical-scavenging activity differed significantly between the two mills. The essential oil distilled from the powders did not: at 0.06 to 0.15 per cent, volume on weight, it varied with neither the mill nor the moisture to a significant degree.
Conditions: Hammer mill and pin mill; seed at 6.4 to 13.6 per cent moisture (dry basis)
What this does not show: One lot of market seed, ground at room temperature in one laboratory machine fitted as each mill. The oil contents are low for coriander and the paper gives no figure for the whole seed, so it shows no difference between the two mills, not how much oil either lost. The authors note that their values are below those they had measured in cold-ground coriander.
Measured on the spice
Grinding · Decreases Cuminaldehyde, γ-Terpinene, p-Cymene, β-Pinene, volatile oil, yield
Measured against the whole seed, cumin ground at room temperature gave about a quarter less volatile oil on distillation: 3.0 per cent against 4.0 in the genotype GC 4 and 2.5 against 3.3 in RZ 209, losses the authors give as 23.2 and 24.3 per cent. Seed chilled to −30 °C with liquid nitrogen before grinding gave 4.1 and 3.6 per cent, a little more than the whole seed, which the authors put down to oil being easier to distil out of a powder. Cuminaldehyde was the main constituent of every oil. In GC 4 it made up 48.2 per cent of the oil after ordinary grinding and 56.1 per cent after cold grinding; in RZ 209 the two were close, 69.7 and 71.6 per cent. The lighter terpenes did not follow it: β-pinene, γ-terpinene and p-cymene each made up a smaller share of the oil from cold-ground GC 4 than from the ordinary grind.
Conditions: Room temperature in a domestic mixer grinder; −30 °C under liquid nitrogen in a pin mill · 50 to 100 µm from the cold pin mill; not given for the ordinary grind · Two Indian genotypes, GC 4 and RZ 209; oil distilled in water for 3 h
What it means in practice:Grinding itself costs cumin part of its volatile oil before any storage begins, and keeping the seed cold prevents that loss. What changes in the make-up of the oil is less tidy than the total: the share of cuminaldehyde rose with cold grinding, and the shares of several lighter terpenes fell.
What this does not show: The ordinary grind was made in a kitchen mixer grinder and the cold grind in a pin mill, so machine and temperature changed together. The temperature reached in ordinary grinding and the fineness it gave are not reported. Two genotypes, three replicates, and composition as shares of the oil, not amounts in the seed.
Measured on the spice
Grinding · Depends on conditions dietary fibre, protein, yield
Roller milling split fenugreek seed into a fibre-rich husk and a protein-rich flour, and the split depended on the moisture to which the seed had been conditioned. As conditioning moisture rose from 12 to 20 per cent, coarse husk increased from 33.75 to 42.46 per cent and flour fell from 49.52 to 41.62 per cent. At 16 per cent the husk fraction, 40.87 per cent of the seed, held 73.4 per cent dietary fibre, and the flour held 41.83 per cent protein and 13.22 per cent fat, against 22.5 per cent protein and 51.25 per cent fibre in the whole seed.
Conditions: Seed conditioned to 12 to 20 per cent moisture before roller milling
What this does not show: Read in the abstract only. A study of fractionation for food ingredients; it reports nothing about the flavour of either fraction.
Measured on the spice
Grinding · Retains volatile and non-volatile metabolites (untargeted), particle size
A metabolomic comparison of ginger powders of different particle size concluded that particle size was not a decisive factor in the variation of their volatile and non-volatile compounds. The compounds that did distinguish the powders pointed to geographical origin and to processing, specifically drying, as the stronger influences.
Conditions: Ginger powders of different particle size compared by volatile and non-volatile metabolite profiling
What this does not show: Read in the abstract only, which gives no data and no particle sizes. It describes freshly prepared powders and says nothing about how fine and coarse powders age.
Measured on the spice
Cryogenic grinding · Retains volatile oil, colour
Black pepper, White pepper, Green peppercorn
For black, white and green pepper alike, cryogenic grinding preserved the main potent aroma compounds better than hammer milling and did minimal damage to colour and sensory character. In both kinds of ground pepper, however, the concentrations of the main aroma compounds were dramatically reduced after six months of storage at 4 °C.
Conditions: Cryogenic grinding against hammer milling; ground samples then stored at 4 °C for 6 months
What this does not show: Read in the abstract only, which gives no figures. However gently the pepper was milled, the ground product still lost aroma in cold storage, so the advantage of cold milling is a head start, not protection.
Measured on the spice
Cryogenic grinding · Retains volatile oil
Cinnamon (Ceylon), Cumin, Nutmeg, Oregano, White pepper
Cinnamon, cumin, nutmeg, oregano and white pepper milled cryogenically retained more of their volatile components than the same spices milled at ambient temperature, and untrained observers could smell the difference in some of them.
Conditions: Cryogenic against ambient milling; gas chromatography and untrained sensory observers
What this does not show: Read in the abstract only, which does not say how large the difference was or in which of the five spices observers could detect it.
Measured on the spice
Cryogenic grinding · Depends on conditions particle size
Fenugreek ground under cryogenic and ambient conditions at 5 to 15 per cent moisture gave average particle sizes from 0.31 to 0.80 mm and specific energy consumption from 8.37 to 50.17 kWh per tonne across the conditions tested. The comparison showed that ambient grinding needed more power and more specific energy than cryogenic grinding.
Conditions: Average particle size 0.31 to 0.80 mm · Seed at 5 to 15 per cent moisture (wet basis), ground under cryogenic and ambient conditions
What this does not show: Read in the abstract only, which gives ranges across all conditions and does not say which moisture or method produced which value. It measured the grinding, not the flavour of the powder.
Measured on the spice
Cryogenic grinding · Depends on conditions colour, particle size
Turmeric ground cryogenically was found better in colour than turmeric ground in a hammer mill at ambient temperature. The two powders also differed in how they pack and flow: tap density ran from 678.7 to 546.7 kg/m³ for the cryogenically ground grades against 642.3 to 468.6 kg/m³ for the ambient ones, and the angle of repose from 26.85 to 34.0° against 23.10 to 28.06°.
Conditions: Cryogenic grinder compared with a hammer mill at ambient temperature; rhizome at 4 to 10 per cent moisture (wet basis)
What this does not show: Read in the abstract only, which says the colour was better without giving colour values or curcumin content. One cultivar.
Measured on the spice
Drying
To make black pepper, the picked spikes are described as being left in heaps overnight for what the handbook calls a brief fermentation, then spread on bamboo mats or concrete floors in the sun and raked regularly. The fruit wall shrinks and the berries come away from the stalk during raking, or are threshed by treading or by machine. After four to five days the peppercorns are black, dry and wrinkled, with a moisture content usually between 10 and 14 per cent. An alternative is to blanch the spikes and dry them on a flat-bed dryer, which the account says reduces drying time to about seven hours. Dried black pepper weighs about 33 per cent of the fresh fruit.
Conditions: in air · Sun-drying for 4 to 5 days; about 7 h on a flat-bed dryer after blanching · Final moisture usually 10 to 14 per cent
What this does not show: A description of practice in South-East Asia in the 1990s. It does not say what happens in the overnight heap, and no study of that step was read; the blackening is not shown here to be microbial.
Documented practice
Drying · Retains Piperine, pungency, drying time
Fresh ripe Kampot pepper held 38.5 mg of piperine per gram. Oven drying at 55 or 65 °C, with or without boiling beforehand, did not change the piperine content significantly. The drying rate constant almost doubled between 55 and 65 °C, and after drying to constant mass the berries held about 0.02 kg of water per kilogram of dry matter whatever the conditions. The authors suggest piperine survives because it sits mostly in the inner core of the berry and not in the skin.
Conditions: in air · 55 or 65 °C · 8 h of monitored drying, then overnight to constant mass · Ripe red Kampot berries, with or without a boiling pretreatment
What this does not show: Two temperatures only, in a laboratory oven, on ripe red berries. Volatile oil was not measured, so the result says nothing about aroma.
Measured on the spice
Drying · Depends on conditions iron, chromium, volatile oil
A comparison of Brazilian black pepper by drying method and harvest season found that mechanical drying changed the composition of the essential oil, which the authors attribute to the high temperatures reached during processing. Pepper from mechanical dryers with direct heating also carried more iron and chromium, attributed to contact with metal surfaces and to particles from the fire.
Conditions: in air · Brazilian black pepper dried by different methods, including mechanical dryers with direct heating, across harvest seasons
What this does not show: Read in the abstract only, which names no oil constituents and gives no temperatures or piperine figures. The same abstract reports arsenic and lead above legal limits in several samples, a finding about those samples and not about a drying method.
Measured on the spice
Drying · Depends on conditions drying time, volatile oil, moisture
In a laboratory spouted bed dryer, black pepper dried fastest at moderately high temperatures, high air flow and shallow beds. Effective moisture diffusivity rose with temperature, reaching 2.03 × 10⁻¹⁰ m²/s at 75 °C. Essential oil yield from the dried pepper varied significantly with drying temperature between 45 and 75 °C, and the authors chose 65 °C as the best temperature for that dryer.
Conditions: in air · 45 to 75 °C · Laboratory-scale conventional spouted bed dryer; Sri Lankan pepper
What this does not show: Read in the abstract only, which does not give the oil yields behind the choice of 65 °C. One dryer design at laboratory scale.
Measured on the spice
Drying · Decreases drying time, moisture
Thin-layer experiments on black pepper, which leaves the vine at about 65 per cent moisture on a wet basis, were described by a diffusion model with an effective diffusivity between 1.91 × 10⁻¹¹ and 1.22 × 10⁻¹⁰ m²/s and an activation energy of 54 kJ/mol. Halsey’s equation was chosen to estimate the equilibrium moisture of the berries. The authors note that large-scale drying is still done in the open sun or in adapted dryers.
Conditions: in air · Thin-layer convective drying from a harvest moisture of about 65 per cent (wet basis)
What this does not show: Read in the abstract only. An engineering study of water removal; it measured no quality attribute, and the temperatures tested are not stated in the abstract.
Measured on the spice
Drying · Decreases Piperine, drying time, moisture
An ultrasound pretreatment before drying cut the drying time of black pepper from about 601 min in the control to about 445 min, a reduction of 26 per cent, or 19 per cent once the 40 min of pretreatment is counted. The dried pepper reached 9.6 per cent moisture and held 18.64 mg of piperine per gram of dry weight, a loss of about 6 per cent.
Conditions: Pretreatment at 50 °C · 40 min of ultrasound at 35 kHz before drying · Optimised by response surface methodology against an untreated control
What this does not show: Read in the abstract and conclusions only. An optimisation study at laboratory scale; volatile oil was not among the responses reported there.
Measured on the spice
Drying · Depends on conditions chlorophyll, terpenoids, colour, volatile oil, yield
In a trial of cardamom dried at 35, 45 and 55 °C, with and without a dip in 2 per cent sodium carbonate, chlorophyll was best retained in the treated capsules dried at 45 °C, and the loss of total oil was smallest in the same combination. The untreated capsules dried at 45 °C kept the most terpenoids and, when dried continuously, split the least. The authors recommended the alkali pretreatment with continuous drying at 45 °C as the conditions that met trade quality standards.
Conditions: in air · 35, 45 and 55 °C · With or without a 2 per cent sodium carbonate treatment before drying; dried continuously or in stages
What this does not show: Read in the abstract only, which gives no chlorophyll or oil figures. One trial in Sri Lanka in the early 1990s; whether the treatment is permitted or used today is a separate question the study does not address.
Measured on the spice
Drying · Depends on conditions α-Terpinyl acetate, 1,8-Cineole, volatile oil
In small cardamom dried at three temperatures in a hot-air dryer, the two compounds that carry the characteristic aroma were α-terpinyl acetate, at 61.65 to 68.19 per cent of the oil, and 1,8-cineole, at 7.23 to 11.76 per cent. The abstract reports that esters and alcohols changed more with drying time than the other classes of compound.
Conditions: in air · Three temperatures in a hot-air convective dryer
What this does not show: Read in the abstract only, and the indexed abstract is truncated: it does not say which temperature gave which composition. The ranges show how far the two constituents moved across the dried samples, nothing more.
Measured on the spice
Drying · Depends on conditions 1,8-Cineole, monoterpene hydrocarbons, (E)-2-unsaturated aldehydes, volatile oil, yield
Fruit of Amomum tsao-ko dried at six temperatures gave the highest yield of essential oil at 55 °C and low yields at 85 and 100 °C. The composition shifted with temperature as well: the highest temperatures gave oil richer in monoterpene hydrocarbons, lower temperatures gave more (E)-2-unsaturated aldehydes, and eucalyptol (1,8-cineole), the main constituent, accumulated most in the fruit dried at 100 °C.
Conditions: in air · 25, 40, 55, 70, 85 and 100 °C
What this does not show: Read in the abstract only, which gives no yields. Laboratory drying at fixed temperatures, not the fire-drying over which much of this fruit is traditionally cured.
Measured on the spice
Drying · Depends on conditions drying time, moisture
Slices of turmeric 3 mm thick took very different times to reach 10 per cent moisture depending on the method: 28 min in a microwave at 500 W, 90 min under infrared lamps, 355 min in a vacuum oven at 50 °C, 469 min in a convection oven at 50 °C, 610 min in a freeze-dryer and 1100 min in the sun at 30 to 35 °C.
Conditions: in air · Sun at 30 to 35 °C; ovens at 50 °C; microwave at 500 W · Unboiled slices 3 mm thick, dried to below 10 per cent moisture from 79.4 per cent
What this does not show: Thin slices of greenhouse-grown rhizome in 200 g lots, not whole boiled fingers; whole rhizomes dry far more slowly. The times belong to this equipment and load.
Measured on the spice
Drying · Depends on conditions Curcumin, colour
Of six drying methods applied to the same sliced turmeric, freeze-drying and microwave drying left the most curcumin, 3.8 per cent, and sun-drying the least, 2.6 per cent. Colour followed the same order: the freeze-dried powder was the lightest and yellowest (L* 74.0, b* 63.8, browning index 17.07), the sun-dried the darkest and reddest (L* 48.7, b* 51.0, browning index 36.3), and the oven, vacuum, infrared and microwave samples did not differ significantly from one another in browning. Yellowness and chroma correlated strongly with curcumin content (r = 0.92). The authors attribute the poor result in the sun to light, heat and oxygen acting together over a long drying time.
Conditions: in air · Sun at 30 to 35 °C against oven, vacuum, infrared, microwave and freeze-drying · Unboiled slices 3 mm thick
What this does not show: Unboiled slices of hydroponically grown turmeric; commercial turmeric is boiled before drying, which changes how the pigment is distributed. One trial, three replicates. The explanation offered for the sun-dried result was not tested.
Measured on the spice
Drying · Depends on conditions Zingiberene, ar-turmerone, β-turmerone (curlone), α-santalene, β-sesquiphellandrene, volatile oil
Essential oil yield was highest from freeze-dried turmeric, 4 per cent by volume, followed by microwave-dried at 3.3 per cent and infrared-dried at 2.7 per cent; sun, convection oven and vacuum oven did not differ significantly from one another. The oils fell into two groups. Freeze-dried and sun-dried turmeric kept large shares of sesquiterpene hydrocarbons, with α-zingiberene at 11.4 and 10.3 per cent and ar-turmerone at about 30 per cent. Oils from the four heated methods held only 2.4 to 3.5 per cent α-zingiberene and 49 to 53 per cent ar-turmerone, with sesquiterpene hydrocarbons falling from about 40 per cent to 13 to 16 per cent of the oil.
Conditions: in air · Six drying methods on unboiled slices; oil by hydrodistillation, composition as peak area
What this does not show: Compositions are shares of the oil by peak area, so a rise in ar-turmerone can reflect the loss of other constituents as much as a gain. Greenhouse-grown, unboiled slices from one harvest.
Measured on the spice
Drying · Decreases drying time, moisture, water activity
Turmeric slices dried under simulated sunlight reached a final moisture of 6.23 to 8.54 per cent and a water activity of 0.331 to 0.365, in 14.22 h at 40 °C and 3.17 h at 70 °C. The light raised the temperature inside the slices about 10 °C above that of the drying air within three hours. Of five thin-layer models, the Page model was chosen as the best description, with a rate constant that rose significantly with temperature and did not differ between a UV-blocking and a UV-transmitting cover. Effective moisture diffusivity rose from 0.45 to 1.07 mm²/h between 40 and 70 °C under the UV-blocking cover, giving an activation energy of about 21.5 kJ/mol.
Conditions: in air · 40, 50, 60 and 70 °C under simulated sunlight · 14.22 h at 40 °C; 7.50 h at 50 °C; 4.75 h at 60 °C; 3.17 h at 70 °C · Unboiled slices 2 mm thick, initial moisture about 84 per cent (wet basis)
What this does not show: A laboratory dryer with lamps standing in for the sun and thin unboiled slices. The figures describe that apparatus and should not be read as drying times for a solar dryer in the field.
Measured on the spice
Drying · Depends on conditions Curcumin, demethoxycurcumin, bisdemethoxycurcumin, colour
Under simulated sunlight, the turmeric that lost curcumin was the turmeric that dried slowly. At 40 °C curcumin fell significantly under both covers, from 197.03 to 182.50 mg/g of dry solids under the UV-blocking cover and from 211.97 to 184.99 mg/g under the UV-transmitting one, and total curcuminoids fell with it. At 50 and 70 °C the changes were not significant, and at 70 °C under the UV-blocking cover no curcuminoid was lost. The authors relate the losses to the accumulated heat load, which was highest in the longest runs. The powder dried at 70 °C was nonetheless the darkest, with the lowest lightness and yellowness under both covers.
Conditions: in air · 40 to 70 °C under simulated sunlight · UV-blocking polycarbonate or UV-transmitting acrylic cover; curcuminoids before and after drying
What it means in practice:In this experiment a quick, hotter drying protected the pigment better than a long, cool one in the light, at some cost to the brightness of the powder.
What this does not show: Thin unboiled slices under lamps. The fresh samples for each run differed in curcuminoid content, so each comparison is within a run. One significant loss was also recorded at 60 °C under the UV-blocking cover, which does not fit the trend neatly.
Measured on the spice
Drying
To prepare dried ginger, the washed rhizomes are described as being killed either by immersion in boiling water for ten minutes or by peeling, scraping or slicing, and then dried, usually in the sun for several days. Ginger with the peel carefully scraped off is traded as uncoated or white ginger and ginger with the peel retained as coated or black ginger; uncoated ginger is sometimes treated with lime to whiten it and to reduce insect attack. The handbook notes that oil yields are higher from coated rhizomes because the outer tissue is rich in oil cells, and that poor handling after harvest can substantially reduce the pungent compounds.
Conditions: in air · Immersion in boiling water for 10 min where that method is used; sun-drying for several days
What this does not show: A handbook description from the 1990s with no drying temperatures or final moisture. It reports what is done and the reasons given.
Documented practice
Drying · Converts Gingerol, Shogaol, pungency
Ginger dried in the open sun held more 6-, 8- and 10-gingerol than ginger dried in a solar tunnel or a hot oven, and less of the corresponding shogaols. Raising the oven temperature from 120 to 150 °C increased the shogaols sharply; at 180 °C both gingerols and shogaols fell, which the authors attribute to degradation and polymerisation. At 150 °C the shogaol content rose with drying time up to 6 h and dropped at 7 h. The order of shogaol formation was oven at 150 °C, then solar tunnel, then open sun.
Conditions: in air · Open sun at 23 to 34 °C; solar tunnel at 31 to 47 °C; oven at 120, 150 and 180 °C · Nine days in the sun; up to 7 h in the oven · Sliced rhizomes dried to about 10 per cent moisture
What this does not show: The oven temperatures are far above those used to dry ginger for the spice trade, so the oven results show the direction of the chemistry and not a commercial product. The values sit in a table and figures; the text read gives the comparisons and not every number. One source of rhizomes.
Measured on the spice
Drying · Decreases volatile oil
The essential oil content of dried ginger was highest after open-sun drying, lower after solar-tunnel drying and lowest after oven drying at 150 °C. The difference between sun and tunnel was not significant; the fall in the oven was, and the authors attribute it to evaporation and decomposition of the oil at the higher temperature.
Conditions: in air · Open sun at up to 34 °C; solar tunnel at up to 47 °C; oven at 150 °C
What this does not show: The oil contents are shown in a figure and are not quoted in the text read. The oven temperature tested is far hotter than commercial ginger drying. Sun-drying for nine days carries risks the study did not assess, such as contamination and mould.
Measured on the spice
Drying · Depends on conditions Gingerol, Shogaol, volatile oil
Ginger powder of the variety Xiaolin Huangjiang dried in two stages, 90 min at 120 °C followed by 150 min at 80 °C, held 11.87 mg/g of the gingerol group measured (6-, 8- and 10-gingerol and 6-shogaol), against 7.12 mg/g after 360 min at a constant 80 °C. The slower constant drying kept far more volatile oil: 3.46 per cent against 1.29 per cent.
Conditions: in air · 120 °C then 80 °C, against a constant 80 °C · 90 min plus 150 min, against 360 min
What it means in practice:A drying schedule that keeps ginger’s pungent compounds is not necessarily the one that keeps its aroma; in this comparison the two pulled in opposite directions.
What this does not show: Read in the abstract only. The figures given are for one of three varieties, and the abstract does not separate gingerols from shogaol in the total.
Measured on the spice
Drying · Depends on conditions Zingiberene, volatile oil
Among ginger dried by hot air, under vacuum, in the sun and by vacuum freeze-drying, the hot-air sample showed the highest content of volatile compounds and, in the authors’ words, the richest odour. The relative content of zingiberene was significantly higher in the hot-air sample than in the others.
Conditions: in air · Hot air, vacuum, sun and vacuum freeze-drying compared by headspace GC-MS and a fast GC electronic nose
What this does not show: Read in the abstract only, which gives no temperatures and no amounts. It disagrees with the study in which sun-dried ginger kept more essential oil than oven-dried ginger; that oven ran at 150 °C, and the two studies measured different things, headspace volatiles here and distilled oil there.
Measured on the spice
Drying · Depends on conditions total phenolics, drying time, moisture, antioxidant capacity
Peeled ginger slices dried at 50, 60 and 70 °C reached their peak drying rate after 7, 6 and 4.5 h, and the peak rate at 70 °C was about twice that at the two lower temperatures. The Midilli model described the moisture ratio best (R² of 0.993 to 0.997), narrowly ahead of the Page model, while the Lewis and Henderson–Pabis models fitted poorly. The browning index did not differ significantly between temperatures. Total phenolics extracted from the dried ginger were highest after drying at 50 °C, 1875.9 mg of gallic acid equivalents per 100 g, against 1468.1 and 1427.1 mg at 60 and 70 °C and 1221.6 mg in fresh ginger.
Conditions: in air · 50, 60 and 70 °C · Peeled slices 3 mm thick in a small hot-air dryer
What this does not show: Supermarket ginger in a domestic-scale dryer. The study measured neither gingerols nor volatile oil, so it does not show what the temperatures did to pungency or aroma.
Measured on the spice
Drying
A review of saffron drying records distinct practices by country. In India the stigmas are dried in the sun for three to five days, to 8 to 10 per cent moisture. In Morocco they are spread thinly on cloth and dried in the sun for several hours or in the shade for seven to ten days. In Italy they are placed on a sieve over oak charcoal and turned halfway through. In Greece they are spread in shallow layers on silk-bottomed trays, held at 20 °C for the first hours and then at 35 to 45 °C until they reach 10 to 12 per cent moisture. Traditional Spanish methods work at 75 to 121 °C for 28 to 55 minutes. In Australia, food dehydrators blowing air at 40 to 55 °C are used.
Conditions: in air · From ambient shade to 75–121 °C, depending on the country · From 28 to 55 min to 7 to 10 days
What this does not show: Second-hand: each national practice is the review’s summary of earlier papers, and practice within a country varies. Iran, the largest producer, is described only as drying in sun or shade at room temperature.
Documented practice
Drying · Increases Safranal
Summarising work that compared three types of drying, the review reports that the safranal detected in saffron increased with drying temperature, in the order oven, then sun, then shade. It sets this beside the account of safranal formation: the compound is absent from the fresh stigma and arises from picrocrocin by enzymatic action or by dehydration under heat, and saffron dried at high temperature has no active enzymes left, so that in such saffron the volatiles come from thermal breakdown.
Conditions: in air · Oven drying at high temperature, sun-drying at ambient temperature, and shade-drying, as compared in the literature reviewed
What this does not show: A review’s summary of other studies, without the figures behind the ranking. More safranal is not the same as better saffron: the same heat acts on the crocins that give the colour.
Review of studies
Drying · Depends on conditions drying time, moisture
Fresh saffron stigmas reached the 12 per cent moisture limit in 45 min in an electric oven at 50 °C and in 30 min in a vacuum oven at the same temperature. In a microwave they took 6 min at 400 W and 3 min at 600 W. All the dried samples fell into the first category of the ISO classification the authors applied.
Conditions: 50 °C in the ovens; 400 and 600 W in the microwave · 45 min, 30 min, 6 min and 3 min respectively · Fresh stigmas dried to below 12 per cent moisture
What this does not show: Small laboratory lots from one harvest day in Zhejiang. The load in the oven is not stated, and drying time depends heavily on it.
Measured on the spice
Drying · Depends on conditions Safranal, Crocin, Picrocrocin, HTCC (4-hydroxy-2,6,6-trimethyl-1-cyclohexene-1-carboxaldehyde)
When the drying time at a given setting was lengthened, crocin and picrocrocin in saffron barely moved while safranal swung widely. In an electric oven at 50 °C, extending drying from 50 to 65 min raised crocin by 1.81 per cent and safranal by 26.90 per cent. At 60 °C, going from 45 to 60 min raised crocin by 1.13 per cent but cut safranal by 23.13 per cent; at 70 °C, 30 to 45 min raised safranal by 13.18 per cent. In a microwave at 600 W, doubling the time from 3 to 6 min cut safranal by 58.59 per cent and crocin by 1.10 per cent while the picrocrocin peak rose by 13.84 per cent. The authors explain the pattern as formation and degradation proceeding at once, at rates that depend on temperature.
Conditions: 50, 60 and 70 °C in ovens; 450 and 600 W in a microwave · Each setting compared at a shorter and a longer time
What this does not show: Percentage changes in chromatographic peak area between two settings, not absolute contents. One harvest day, small lots, no replication across seasons. The changes in safranal do not run in one direction, so the study supports sensitivity, not a rule.
Measured on the spice
Drying · Depends on conditions drying time, moisture
Raising the temperature from 40 to 60 °C shortened the drying of halved chillies by 37 per cent under vacuum, 32 per cent in a freeze-dryer, 67 per cent in hot air and 48 per cent in hot air with microwaves. Doubling the microwave power from 50 to 100 W cut the time by a further 39 per cent at 40 °C and about 50 per cent at 60 °C. The shortest run, 70 min, was hot air with 100 W of microwaves at 60 °C; the longest, 1010 min, was vacuum drying at 40 °C. Of seven thin-layer models, the Midilli equation described every method best, with R² of 0.999.
Conditions: 40 and 60 °C · From 70 min to 1010 min · Halved, deseeded fruit dried to 10 per cent moisture by convective, convective-microwave, vacuum and freeze-drying
What this does not show: One cultivar, halved and deseeded, in 100 g lots on laboratory equipment. Whole pods with their waxy skin intact dry far more slowly, as other studies recorded here show.
Measured on the spice
Drying · Depends on conditions total carotenoids, colour
Total carotenoids in dried chilli were highest after freeze-drying, slightly lower after vacuum drying, lower again after hot air and lowest after hot air with microwaves at 100 W. Raising the temperature from 40 to 60 °C lowered the carotenoid content in every method. Retention ranged from about 84.4 per cent after freeze-drying at 40 °C to about 57.6 per cent after microwave-assisted drying at 60 °C and 100 W. Freeze-dried and vacuum-dried chillies were also the brightest and reddest. The authors attribute the advantage of the two low-pressure methods mainly to the absence of oxygen.
Conditions: 40 and 60 °C · Freeze-drying and vacuum drying against hot air and hot air with microwaves
What this does not show: Total carotenoids by one method on one cultivar; individual pigments such as capsanthin were not reported in the sections read. The oxygen explanation is the authors’ interpretation.
Measured on the spice
Drying · Decreases Capsaicin, Dihydrocapsaicin, pungency
Every drying method lowered the capsaicin and dihydrocapsaicin content of chilli below that of the fresh fruit, and in every method the higher temperature lost more. The smallest loss, about 13 per cent, followed freeze-drying at 40 °C; the largest, about 45 per cent, followed hot air with 100 W of microwaves at 60 °C. Freeze-drying and vacuum drying did not differ significantly and kept the most.
Conditions: 40 and 60 °C · Freeze-drying, vacuum, hot air, and hot air with 50 or 100 W of microwaves
What this does not show: One cultivar, halved and deseeded, so that the inner tissue was exposed to the drying air. It conflicts with studies of whole pods in which hotter, faster drying left more capsaicinoid than slow drying; the material and the range of temperatures differ.
Measured on the spice
Drying · Depends on conditions Capsaicin, Capsanthin, Dihydrocapsaicin, pungency, colour
Whole chillies of two Guizhou varieties held significantly more capsaicin and dihydrocapsaicin after hot-air drying at 75 °C for 12 h than after five days in the sun or twelve days in the shade; the highest content, 1.71 mg/g, was in hot-air-dried Xianjiao. Capsanthin followed the same order, highest after hot air and lowest after shade-drying. The authors attribute the result to time: the slow methods leave enzymes active and oxidation running for days.
Conditions: in air · Hot air at 75 °C; sun at 25 to 33 °C; shade at 18 to 25 °C · 12 h; about 5 days; about 12 days · Two Guizhou varieties, whole fruit dried to about 7 per cent moisture
What it means in practice:For a whole chilli, the long exposure of slow drying can cost more pigment and pungency than the heat of a quick one.
What this does not show: One season and three treatments that differ in several ways at once. The same study found shade-drying gave the richer aroma profile, so the ranking depends on what is valued. Conflicts with the finding on halved chillies that higher temperature lost more capsaicinoid.
Measured on the spice
Drying · Depends on conditions drying time, colour
A long, thin chilli type took 112 h to dry at 50 °C, 40 h at 60 °C, 18 h at 70 °C and 13 h at 80 °C; starting at 80 °C and stepping down to 60 °C took 17 h. A small millet type took 33, 20, 10 and 7 h at the four constant temperatures, and a bullet type 48, 38, 20 and 9 h. The peppers dried at 70 and 80 °C had darker surfaces, and the authors judged those dried at a constant 50 °C or by the stepped programme to have kept the brightest colour.
Conditions: in air · Constant 50, 60, 70 and 80 °C, and stepped from 80 °C down to 60 °C · From 7 h to 112 h · Whole fruit of three Chinese chilli types
What this does not show: Whole fruit in one laboratory dryer; the times belong to those three types at their own target moistures of 10 to 14 per cent. Colour was measured on the surface, not as extractable colour.
Measured on the spice
Drying · Depends on conditions Capsaicin, pungency
In whole chillies dried in hot air, the measured capsaicin content was lowest after drying at 50 °C and highest after drying at 80 °C in two of three types: 1.77 per cent against 2.34 per cent in the long thin type and 2.33 per cent against 2.97 per cent in the millet type. The bullet type ranged only from 2.08 per cent at 70 °C to 2.24 per cent at 80 °C. The authors attribute the higher values at 80 °C to the much shorter drying time and to inactivation of peroxidase.
Conditions: in air · 50 to 80 °C · Whole fruit of three chilli types; capsaicin by a colorimetric method
What this does not show: The assay is colorimetric and less specific than chromatography, and its figures run higher than chromatographic values usually do. The explanation offered was not tested. Conflicts with the study of halved chillies in which the higher of two temperatures lost more capsaicinoid.
Measured on the spice
Drying · Decreases microbial load
Peppers that were blanched and dried in the solar dryer carried significantly lower aerobic mesophilic and coliform counts than peppers dried in the open sun, with or without blanching. Across all samples the aerobic counts ranged from 4.6 to 6.7 and the coliform counts from 1.8 to 3.5 on the scale the paper reports. The authors note that drying controls growth by lowering water activity but may leave spores alive.
Conditions: in air · Blanched or unblanched peppers dried in a natural-convection solar dryer or in the open sun
What this does not show: The paper gives the counts as cfu/g, although the figures read as logarithms; they are used here only to show the direction. One trial, and no pathogen was tested for.
Measured on the spice
Drying · Depends on conditions aflatoxins, patulin, penicillic acid, moisture, water activity, microbial load
Peppers leaving six traditional smoke dryers held 11.0 to 16.3 per cent moisture at a water activity of 0.513 to 0.611, with significant differences between dryers. Fungal counts ranged from 2.6 to 5.7 log CFU/g, and aflatoxin-producing fungi were detected in every dryer by real-time PCR at 2.00 to 3.42 log CFU/g. No mycotoxin was detected in the dried peppers themselves. Among 67 mould isolates, strains of Penicillium expansum, Penicillium thomii and one of Aspergillus parasiticus were able to produce patulin, penicillic acid and aflatoxins respectively.
Conditions: in smoke · Dried peppers sampled from six traditional La Vera dryers belonging to four producers
What it means in practice:The fungi able to make toxins were present on the dried peppers; what kept them from doing so was the low water activity the drying had reached.
What this does not show: Read in the abstract only. Six dryers in one region and one season; it shows what was found there, not the safety of any product.
Measured on the spice
Drying · Decreases Carvacrol, Thymol, γ-Terpinene, volatile oil
Fresh Polish oregano held 33.0 g of volatiles per kilogram, with carvacrol, thymol and γ-terpinene the main components. Drying lowered the total whatever the method, but by very different amounts: to 10.2 g/kg after convective drying at 60 °C, 13.1 g/kg after convective pre-drying with a vacuum-microwave finish, and 27.9 g/kg after vacuum-microwave drying alone.
Conditions: Convective drying at 60 °C · Compared with vacuum-microwave drying and with convective pre-drying followed by a vacuum-microwave finish
What this does not show: Read in the abstract only, which does not state the basis (fresh or dry weight) of the figures or the fate of the individual compounds. One lot of oregano.
Measured on the spice
Drying · Decreases α-Pinene, 1,8-Cineole, bornyl acetate, camphene, volatile oil, drying time
Fresh rosemary held 135 g of volatiles per kilogram, chiefly α-pinene, bornyl acetate, camphene and 1,8-cineole. Convective drying lowered the total to 87.2 g/kg and vacuum-microwave drying to 61.9 g/kg. The combined method, convective pre-drying finished under vacuum-microwave, kept 100 g/kg and took about 30 min, and was rated well by a sensory panel.
Conditions: Convective, vacuum-microwave, and convective pre-drying with a vacuum-microwave finish
What this does not show: Read in the abstract only. The ranking of methods here is the reverse of that found for oregano by the same group, so the result belongs to rosemary and should not be generalised to leafy herbs.
Measured on the spice
Drying · Decreases Eugenol, Linalool, methyleugenol, eucalyptol (1,8-cineole), volatile oil, drying time
Fresh sweet basil held 32.1 g of volatiles per kilogram, with methyleugenol, eugenol, eucalyptol and linalool the main components. Both convective and vacuum-microwave drying brought the total down to 14.4 g/kg, less than half. Convective pre-drying at 40 °C followed by a vacuum-microwave finish at 360 W kept 16.7 g/kg and gave dried basil in which a panel still found strong fresh and floral notes.
Conditions: Combined method at 40 °C and 360 W · About 250 min for the combined method
What this does not show: Read in the abstract only. The best method still lost about half of the volatiles, and the abstract does not say which compounds were lost most.
Measured on the spice
Drying · Depends on conditions Linalool, Eugenol, volatile oil
Of three ways of drying basil, air drying at room temperature brought about only small losses of volatile components, while oven drying at 45 °C and freeze-drying both decreased the total considerably. Linalool was the major component, followed by eugenol. The odour changed in kind as well as strength: fresh basil was described as fresh, herbaceous and floral, the dried samples as mentholated, spicy, hay-like and earthy.
Conditions: in air · Oven at 45 °C; air at room temperature; freeze-drying
What this does not show: Read in the abstract only, which gives no amounts. Its finding that freeze-drying lost much of the volatiles runs against the common assumption that freeze-drying preserves aroma best, and other studies of other basils may differ.
Measured on the spice
Drying · Depends on conditions Linalool, 1,8-cineole, methyl cinnamate, anthocyanins, total phenolics, volatile oil, colour
Across fresh and dried leaves of a purple basil, the three main volatiles spanned very wide ranges: linalool from 81.19 to 1176.09 µg per gram of dry weight, 1,8-cineole from 45.15 to 816.16 µg/g and methyl cinnamate from 13.20 to 637.65 µg/g. The drying method changed the composition of the volatiles significantly, and microwave drying gave a profile distinct from the others. Raising the convective drying temperature lowered anthocyanin content, whereas raising the microwave power raised it.
Conditions: Convective drying at 45, 50 and 55 °C; microwave at 350, 460 and 600 W · Also freeze-drying and sun-drying; Arapgir purple basil
What this does not show: Read in the abstract and conclusions only. The abstract gives ranges across all samples and does not say which method produced which value, so no ranking of methods is taken from it.
Measured on the spice
Drying · Retains Menthol, menthone, volatile oil, yield, moisture
Peppermint left to wilt on the ground before final drying at 30 °C showed only slightly lower essential oil levels than peppermint dried directly at 30 °C, by 7.7 per cent after one day and 1.5 per cent after five, with no change in oil quality. The wilting removed much of the water, reducing the energy needed for the final drying. Oil yield rose from early to full and late bloom, and the compounds that carry the flavour, menthol and menthone, were at their best at full bloom, at 43 to 54 per cent and 12 to 30 per cent of the oil.
Conditions: in air · Final drying at 30 °C · One or five days of wilting on the ground beforehand · Peppermint grown in Norway, three seasons
What this does not show: Read in the abstract only. Peppermint grown for oil in a cool climate; the abstract excludes the 50 and 70 °C treatments from its averages without giving their results.
Measured on the spice
Drying · Depends on conditions 1,8-Cineole, (Z)-3-hexenal, 3-(methylthio)propanal, phenylacetaldehyde, dimethyl sulfide, borneol, myrcene
In garden sage whose key odorants had been quantified fresh, drying at 50 °C left all the monoterpenes nearly unchanged. The losses fell on other compounds: very volatile ones such as dimethyl sulfide and 2- and 3-methylbutanal decreased, and 3-(methylthio)propanal, phenylacetaldehyde and the green-smelling (Z)-3-hexenal were lost almost completely. Six commercial dried sages had lower concentrations of the key odorants and of total volatiles than the sage dried in the laboratory.
Conditions: in air · 50 °C
What this does not show: Read in the abstract only. One plant grown in a greenhouse and dried under controlled conditions; the commercial samples differ from it in origin and age as well as in drying.
Measured on the spice
Drying · Depends on conditions Allicin, soluble pectin, reducing sugar, colour, texture
Among five ways of drying garlic slices, pulsed vacuum drying gave the smallest colour change and the highest allicin content, between 8.0 and 252.3 per cent higher than the other techniques. Vacuum freeze-drying kept the slices whole, with the least shrinkage and the best appearance. Infrared drying produced the densest structure and an additional loss of colour and of the compounds measured. The Weibull model fitted the drying curves with R² above 0.99.
Conditions: Vacuum freeze-drying, air impingement, humidity-controlled hot air, pulsed vacuum and infrared drying
What this does not show: Read in the abstract and conclusions only. The allicin figure is a range of advantage over four other methods, not a content. The authors note that the best-performing method was also the slowest.
Measured on the spice
Drying · Decreases pyruvic acid (as an index of pungency), vitamin C, pungency, water activity
Pungency, measured as the pyruvic acid released when the onion is crushed, fell as the drying temperature rose. Fresh onions of the three varieties gave 12.16, 10.07 and 9.17 µmol/ml; after drying at 70 °C they gave 6.4, 4.9 and 4.99 µmol/ml, a loss of 47.4, 51.3 and 45.6 per cent. Vitamin C and the sensory scores declined with temperature in the same way, while water activity and pH fell, which the authors count as an advantage for keeping quality. They attribute the loss of pungency to damage to the cells and to loss of the enzyme alliinase at higher temperatures.
Conditions: in air · 50, 60, 70, 80 and 90 °C · 5 h at 70 °C · Three Ethiopian varieties, oven-dried slices milled to powder
What this does not show: Pyruvic acid is an index of the flavour reaction, not a measure of the sulphur volatiles themselves. Three varieties in one laboratory oven; the explanation for the loss was not tested.
Measured on the spice
Drying · Depends on conditions amides (total), volatile oil, colour, drying time
Comparing three drying technologies for Sichuan pepper, microwave vacuum drying was the fastest and retained the most volatile oil, while pulsed vacuum drying retained the most of the amides responsible for the tingle. Both kept colour better than hot air, which the authors attribute to the vacuum limiting browning. The share of husks that split open rose with temperature and correlated with volatile oil content.
Conditions: Best overall result at 60 °C · Microwave vacuum drying at −90 kPa, pulsed vacuum drying and hot-air drying
What this does not show: Read in the abstract and conclusions only, which give no oil or amide contents. The abstract speaks of amides as a group and does not single out hydroxy-α-sanshool.
Measured on the spice
Drying · Depends on conditions total alkylamides, total volatile organic compounds, volatile oil, colour
Of four ways of drying Hanyuan Sichuan pepper, sun-drying gave the lowest total volatile content and the lowest antioxidant activity. Hot air at 50 °C gave the highest total volatile content, and raising it to 60 °C lowered that significantly. Vacuum freeze-drying gave the best colour and the highest total alkylamide, phenolic and flavonoid contents.
Conditions: in air · Hot air at 50 and 60 °C · Also sun-drying and vacuum freeze-drying; Hanyuan Zanthoxylum bungeanum
What this does not show: Read in the abstract only, which gives no figures and reports alkylamides as a total. One cultivar from one region.
Measured on the spice
Drying · Retains Hydroxy-α-sanshool, polyphenols, flavonoids, volatile oil
Sichuan pepper given a radio-frequency heating step before hot-air drying at 50 °C showed no loss of hydroxy-α-sanshool attributable to the radio-frequency step, and kept an aroma profile similar to the fresh spice. The combined treatment also reduced the loss of polyphenols and flavonoids at the higher drying temperatures.
Conditions: Hot air at 50, 55 and 60 °C · With or without radio-frequency heating beforehand
What this does not show: Read in the abstract only. It reports the absence of a negative effect at one condition, not sanshool contents, and does not report microbial reduction.
Measured on the spice
Drying · Decreases Limonene, geranial, neral, citronellal, geranyl acetate, sabinene, β-myrcene, volatile oil, water activity
Limonene, the main volatile of andaliman, fell from 28 093 µg per gram of solids in the fresh fruit to between 19 299 and 21 857 µg/g after drying, depending on the process. Limonene, geranial, α-pinene, sabinene, β-myrcene and (E)-2-hexenal tended to decrease, while geranyl acetate, citronellal and neral tended to increase. Drying significantly altered the citrus, orange-peel, green, warm and lime-leaf notes. The authors proposed oven drying as the best of the five methods for its short duration, low water activity, high volatile content and the liking scores it received.
Conditions: Five drying processes compared; oven drying judged best by the authors
What this does not show: Read in the abstract only, which does not give the conditions of the five processes. The tingling amides of andaliman were not part of this study.
Measured on the spice
Drying
After harvest the clove clusters are described as being separated into buds and stems, both of which are dried in the sun for several days. The dry weight of buds and stems is about a third of the fresh weight, and the dried product is sold in bags.
Conditions: in air · Several days in the sun
What this does not show: A brief handbook description without temperatures, final moisture or any measurement of oil.
Documented practice
Drying
For Ceylon cinnamon, the strips of bark taken from the shoot are described as being packed together, wrapped and left overnight for what the handbook calls a slight fermentation, which makes it easier to scrape off the outer bark. The curled pieces of inner bark are then assembled into compound quills a metre long, the best and longest on the outside and smaller pieces within, and dried in the shade until they are yellowish-brown. They are sometimes bleached with sulphur. The handbook adds that bark intended for distilling should not be allowed to become damp, because mould or fermentation then affects the composition of the oil.
Conditions: in air · Wrapped overnight before scraping · Quills assembled to 1 m and dried in the shade until yellowish-brown
What this does not show: A handbook description of Sri Lankan practice in the 1990s. Nothing is measured, and no study of what happens in the overnight rest was read.
Documented practice
Drying
The nutmeg seed is described as being dried in its shell, often above a slow-burning, smoking fire, or in the sun where only small quantities are handled. The fire is said to deter insects; in the sun there is a danger of overheating, in which the fat of the seed may melt and the kernel then breaks at shelling. A properly dried kernel rattles in its shell. Indonesian nutmegs are often white from a lime treatment against insects. The aril is dried, mostly in the sun, to give mace, and is then stored in the dark, where its colour changes from red to orange-yellow.
Conditions: in smoke · Seed dried in the shell over a slow smoking fire, or in the sun for small quantities; aril dried in the sun
What this does not show: A handbook description from the 1990s. It gives no temperatures, and the colour change of mace in the dark is stated, not measured.
Documented practice
Drying
For use as a spice, harvested star anise fruits are described as being placed in flat baskets, exposed to the sun for about ten days and then kept in a cool, dry place before they are traded.
Conditions: in air · About 10 days in the sun
What this does not show: A brief handbook description, without final moisture or any measurement of oil.
Documented practice
Drying · Depends on conditions α-phellandrene, dill ether, dillapiole, β-pinene, γ-terpinene, volatile oil
How drying changed dill herb oil depended on the genotype. Shade drying gave the highest α-phellandrene, 57.49 and 55.51 per cent of the oil in two genotypes, and was the better treatment for most components in two others; oven drying at 40 °C gave the highest oil yield, 1.86 per cent, in one genotype, and the most dill ether in another. Drying at 60 °C lowered the oil content of sensitive genotypes while raising dillapiole in some.
Conditions: in air · Shade drying, or a forced-air oven at 40 or 60 °C · Leaves and flowers of six Iranian genotypes grown in one field, harvested at full bloom and dried to 10–12 per cent moisture before distillation
What this does not show: One season, one field and three drying treatments, analysed as a biplot, so not every treatment mean is given in the text. The components analysed did not include limonene or carvone, which lead some dill weed oils, and no sensory test was made.
Measured on the spice
Drying · Decreases drying time
In the hybrid solar dryer, a 1 cm layer at 70 °C dried fastest, and drying at 70 °C cut the drying time of a 1 cm layer by 66.67 per cent compared with 50 °C. The solar dryer performed comparably to the oven.
Conditions: in air · 50, 60 and 70 °C in a hybrid solar dryer and an oven · Fresh leaves at about 82 per cent moisture, spread in layers 1, 2 or 3 cm deep
What this does not show: Drying behaviour only: aroma, essential oil and colour were not measured, so the study does not show which conditions give the better herb. Some percentage reductions reported in the results section exceed 100 per cent, so only the figure in the abstract is used.
Measured on the spice
Drying
The fruit is dried to be used as a seasoning, and the dried slices are the asam keping of the market. The traditional way is to lay the material on mats in an open space, directly under the sun. Engineers describing it name its weakness as the weather: the quality of what is dried cannot be controlled, because the drying depends on the conditions of the day.
Conditions: in air · Slices laid on mats in the open, directly under the sun, as described for Malaysia
What this does not show: A description in a few sentences by authors whose subject was their own dryer. It gives no drying time, no slice thickness and no account of how producers judge that the slices are dry.
Documented practice
Drying · Depends on conditions moisture
How dry the slices came out depended on how ripe the fruit was as well as on how long it was dried. Averaged over the three drying times, slices from unripe fruit held 13.8 per cent water, from half-ripe fruit 16.2 per cent and from ripe fruit 19.9 per cent. Averaged over ripeness, 12 hours left 19.0 per cent, 13 hours 16.5 per cent and 14 hours 14.4 per cent. The fresh fruit itself differed little, at 89 to 90 per cent water, but the ripe fruit was heavier, sweeter and slightly less acid, at pH 1.80 against 1.67. The authors judged unripe fruit dried for 12 hours the most acceptable.
Conditions: in air · 50 °C in a cabinet drier · 12, 13 and 14 hours · Slabs about 5 mm thick, cut from unripe, half-ripe and ripe fruit
What it means in practice:It agrees with the practice the handbook records, of picking the fruit full-grown but still green for drying.
What this does not show: A short conference paper on fruit from one farm, dried in a cabinet and not in the sun. It does not say how acceptability was judged, and its figure for the acid content of the fruit is not used because it does not agree with its own water content.
Measured on the spice
Drying · Depends on conditions furfural, 5-methyl-2-furfural, 2-acetylfuran, moisture, water activity, colour
Fresh calyces held 89.4 per cent water. Oven-drying and freeze-drying brought them to 8.9 to 9.6 per cent, at a water activity of 0.40 to 0.48; vacuum-drying left 12.9 per cent and sun-drying 15.6 per cent, at a water activity of 0.73. Every method changed the volatile compounds. Of 74 identified, the terpenes, several aldehydes and the fruity esters of the fresh calyx fell: the peak for linalool, the largest terpene of the fresh calyx, was less than a twentieth as large in every dried sample. Five of the six furans rose instead, furfural most of all, by between 36 and 111 times. The authors expect this to mean less of a fruity, floral and green smell and more of a caramel-like one. Ground vacuum-dried calyx stayed closest in colour to fresh, and its water extract was the nearest in lightness and redness to that of fresh calyx; the extracts of oven-dried, freeze-dried and sun-dried calyx were darker and less red. Under the electron microscope freeze-dried tissue looked most like fresh.
Conditions: in air · 50 °C in two ovens and under vacuum; below 45 °C in the sun; freeze-dried at −40 °C · 12 h in the ovens, 26 h under vacuum, 19 h in the sun, 48 h in the freeze dryer · Whole calyces of the Malaysian cultivar UMKL, dried in a single layer
What it means in practice:The caramel-like note reported in dried roselle is, on this evidence, made in the drying and is not in the fresh calyx: the authors attribute the furans to sugars breaking down under heat at low water content.
What this does not show: One cultivar from one grower, with volatile compounds given as peak areas and not as amounts. The odour descriptions come from reference lists; no panel smelled the samples. The sun-drying was slowed by haze, the sun-dried calyces showed compounds the authors read as signs of fermentation, and they say those results should not be generalised. The fresh and vacuum-dried extracts were also the weakest, at 0.4 and 1.1 per cent soluble solids against 2.8 to 3.8, which bears on their lighter colour.
Measured on the spice
Drying · Depends on conditions Hibiscus acid, glucose, fructose, γ-aminobutyric acid, fumaric acid, moisture
Calyces from sixteen places were each dried two ways. The shade-dried lots averaged 10.5 per cent water and the tray-dried 7.9 per cent. Hibiscus acid was the main compound in a hot-water extract of every lot: 9.8 to 13.2 g per 100 g of dry powder after shade drying and 12.4 to 15.5 g after tray drying, about 12 g and 14 g on average, which the authors put as a loss of almost 15 per cent in the shade. Glucose and fructose were lower in most shade-dried lots too, at about 1.5 to 2.3 g per 100 g each against 2.0 to 2.7 g, while γ-aminobutyric acid and fumaric acid were higher. The authors suggest why: calyces that dry slowly stay damp and warm for days and may begin to ferment. Four of the sixteen shade-dried lots did not show the pattern, which the authors put down to how the drying went and not to where the plants grew.
Conditions: in air · 26–28 °C in the shade; 60 °C in the tray drier · Four days in the shade; six hours in the tray drier · About 50 g of fresh red calyces from each of sixteen places, fifteen in the Garo Hills of Meghalaya and one at Noida
What it means in practice:It does not overturn the handbook’s advice for Africa, which is to dry in the shade because full sun lowers quality. The handbook sets shade against sun; this study set shade against a heated tray at 60 °C, above the 43 °C the handbook gives as the limit for heated dryers, and measured acids and sugars, not colour.
What this does not show: One study, on about 50 g of calyces per lot. The compounds were measured in a five-minute hot-water extract brought to neutral pH, not in the calyx itself, and citric and malic acids were not among those the study assigned. Colour and anthocyanins were not measured. The abstract says all sixteen lots came from Meghalaya; the table of locations places one at Noida, in Uttar Pradesh.
Measured on the spice
Drying · Depends on conditions Malic acid, Citric acid, Anthocyanins, succinic acid, tartaric acid, oxalic acid, colour
Five acids were measured by liquid chromatography in a water extract of the ground calyx. In freeze-dried calyces succinic acid was the largest, at 246 to 325 mg per 100 g of dry weight, then malic at 122 to 153 mg, tartaric at 48 to 60 mg, citric at 7 to 10 mg and oxalic at 1 to 10 mg, about 0.44 to 0.52 g in all. Six days of drying in the sun cut the total by 45 per cent in two varieties and 55 per cent in the third; malic and succinic acid fell most, and citric acid did not fall, standing at 22 to 27 mg. Drying in hot air changed the totals little: they ran from 0.36 to 0.61 g per 100 g across the three temperatures and varieties, and the 70 °C lots were as high as the freeze-dried ones or higher. The acidity of the water extract, by titration, was 37 to 44 per cent lower from sun-dried calyces than from fresh ones. In the two red varieties the sun-dried calyces also gave about 37 per cent less anthocyanin on average, and their extracts were darker.
Conditions: in air · In the sun on concrete; in a tray drier at 50, 60 and 70 °C · Six days in the sun, from nine to five, prolonged by cloud and rain; six to eight hours in the drier · About 10 kg of fresh calyces per lot of three Mexican varieties grown at Acaponeta, Nayarit: Negra Quiviquinta, dark red; UAN-9, light red; UAN-16, white
What it means in practice:The authors put the loss in the sun down to its length: calyces lying damp for six days may have had their acids partly fermented by the organisms on them, where hot air at 50 °C or more dries them in hours. It agrees with the handbook’s caution that drying in the sun can lower quality, and with the Indian study in which slow drying in the shade cost hibiscus acid. Of the methods tried, the authors judged hot air at 70 °C to keep the calyx best.
What this does not show: One harvest of three varieties at one site, with sun-drying that took six days because of cloud where two or three are usual; the authors cite another Mexican study that found no loss of acidity after three days in the sun. Hibiscus acid was not measured, so the five acids add up to about half a gram per 100 g where another study found ten grams or more of hibiscus acid alone. The conclusion gives the average loss of acids in the sun as 49.9 per cent, which is not the mean of the three figures in the text.
Measured on the spice
Blanching · Decreases enzyme activity
β-Glucosidase, the enzyme that splits glucovanillin, was at its highest in the fresh bean and could not be detected after blanching at 70 °C for 5 min or after the sweating stage that followed. Activity reappeared during drying, and the cured bean held 25 per cent of the activity of the fresh one. The authors point out that vanillin was nevertheless accumulating fastest in exactly the stage where no activity could be measured, and they attribute the returning activity to β-glucosidase from microorganisms that colonise the bean after sweating.
Conditions: in water · 70 °C · 5 min · Activity expressed against the fresh bean as 100 per cent
What it means in practice:The simple account in which killing the pod releases its own enzyme onto its own glucovanillin does not fit this measurement on its own: the pod’s enzyme was no longer detectable when most of the vanillin formed.
What this does not show: An assay on extracts from one batch, and “not detected” depends on the sensitivity of the assay. The attribution of the later activity to microorganisms is the authors’ inference, supported by other work but not tested here.
Measured on the spice
Blanching · Decreases enzyme activity
A kinetic study of the β-glucosidase of vanilla beans found its greatest activity at pH 6.5 and 38 °C. Under hot-water treatment the enzyme lost 51 per cent of its activity after 3 min at 60 °C, 60 per cent after 90 s at 70 °C and 48 per cent after 30 s at 80 °C. When beans were cured in an oven at 60 °C for 36 to 48 h, all β-glucosidase activity was lost. A separate laboratory model of curing found no detectable β-glucosidase after scalding for 20 min at 80 °C, while protease and peroxidase remained active, and glucoside levels stayed high sixteen days later.
Conditions: in water · 60, 70 and 80 °C in hot water; 60 °C in an oven · 30 s to 3 min in water; 36 to 48 h in the oven · pH Treated at pH 6.0; optimum activity at pH 6.5
What this does not show: Both papers were read in the abstract only. The figures are for the enzyme under defined laboratory treatments; neither abstract says how much vanillin the beans finally held, and a short commercial scald is milder than the longest treatments tested.
Measured on the spice
Blanching · Depends on conditions total phenolics, total flavonoids, drying time, colour
Ripe pepper berries dipped in boiling water before oven drying dried faster and kept more of their colour than berries dried without the dip. The drying rate constant rose with the pretreatment at both 55 and 65 °C, but boiling for 10 or 15 min gave no significant gain over 5 min. Colour was significantly altered by drying in every case, with the three colour coordinates at about three-quarters of their fresh values in pretreated berries and lower without pretreatment, and the total colour change was significantly smaller after boiling and significantly larger at 65 than at 55 °C. Without the dip, drying halved the total phenolic and flavonoid contents; with it they were preserved. The authors attribute the effect to inactivation of the browning enzymes and to a more open tissue.
Conditions: in water · Boiling water; drying at 55 or 65 °C · 0, 5, 10 or 15 min of boiling · Ripe red Kampot berries of Piper nigrum, dried in a laboratory oven
What this does not show: Ripe red berries from one Cambodian farm, 30 g lots in a laboratory oven. The enzyme explanation was proposed, not measured. The authors note that they did not examine microbiology, which might call for longer boiling.
Measured on the spice
Blanching · Increases Curcumin, polyphenol oxidase, peroxidase, drying time, enzyme activity
Blanching turmeric by a combined hot-air and microwave method before drying shortened the drying time by between 6.35 and 34.92 per cent, depending on how long the blanching lasted. Polyphenol oxidase was entirely inactivated after 8 min and peroxidase after 10 min. At 8 min, the dried turmeric held 20.76 per cent more curcumin than turmeric dried without blanching.
Conditions: 0 to 10 min; best result at 8 min · Hot-air microwave rolling blanching, followed by drying
What it means in practice:The measurement fits the reasons producers give for cooking turmeric before drying: the heat stops the browning enzymes and the rhizome then dries faster.
What this does not show: Read in the abstract only. A novel blanching machine, not the boiling or steaming used on farms. “More curcumin” is relative to unblanched dried turmeric in the same study.
Measured on the spice
Blanching · Decreases vitamin C, drying time, moisture
Red peppers starting at about 75 per cent moisture reached 5 per cent after 13 h in a solar dryer when blanched in 2 per cent salt solution, 16 h when blanched in plain water and 17 h when unblanched. In the open sun every sample took 28 h, whatever the pretreatment. The solar dryer therefore cut drying time by about 49 to 54 per cent. Vitamin C and mineral contents fell significantly after blanching and drying. A consumer panel scored the colour of blanched, dryer-dried peppers at 7.0 on a nine-point scale and that of unblanched, sun-dried peppers at 3.8, with no significant difference in aroma or texture.
Conditions: in water · Blanching at 93 °C; dryer chamber 42 to 69 °C; ambient 28.6 to 40.5 °C · Blanching for 4 min; drying for 13 to 28 h · Plain water or 2 per cent salt solution; natural-convection solar dryer or open sun, in northern Ghana
What this does not show: One purchase of market peppers and one small wooden dryer in one season. Colour was judged by a consumer panel, not measured, and pungency was not assessed.
Measured on the spice
Curing
Curing is described as beginning within a week of harvest and as three linked stages in which the pods lose 70 to 80 per cent of their water and the aroma develops. The pods are immersed once, occasionally twice, in hot water for 30 to 60 seconds, then held for 24 to 48 hours in cloth-lined containers to sweat. For three to five days they are put out in the sun by day and stored by night, and they are then conditioned in closed containers for two to three months, graded, straightened and packed in sealed tins. The same account gives the Mexican process as taking five to six months: at least two months of sun-drying followed by about three months in boxes.
Conditions: Hot water for the first step; sun and closed containers thereafter · Scalding for 30 to 60 s, sweating for 24 to 48 h, conditioning for 2 to 3 months · As described for South-East Asian practice, with the Mexican process given separately
What this does not show: A handbook description of practice as it stood in the 1990s, written mainly from Indonesian and Indian Ocean production. Times differ between regions and curers, and the account gives no temperatures beyond “hot water”.
Documented practice
Curing · Converts Vanillin, glucovanillin, vanillic acid, p-hydroxybenzaldehyde, vanillyl alcohol
In one batch of Hainan vanilla followed through curing, glucovanillin fell from 10.67 per cent of dry weight in the fresh bean to 6.28 per cent after blanching, 0.74 per cent after sweating, 0.20 per cent after drying and 0.17 per cent in the cured bean. Vanillin moved the other way: 0.03 per cent in the green bean, 0.05 per cent after blanching, 2.30 per cent after sweating and 2.69 per cent after drying, with the highest value in the conditioned bean. Most of the vanillin therefore appeared during the six days of sweating. The vanillin gained was much smaller than the glucovanillin lost, which the authors attribute to further oxidation or reduction of vanillin to other compounds; vanillyl alcohol, absent earlier, stood at 0.22 per cent in the dried bean and 0.16 per cent after conditioning.
Conditions: Blanching at 70 °C; sweating in an oven at 55 °C · 5 min blanching, six days of sweating, 36 sunny days of drying, six months of conditioning · One batch of Hainan beans, sampled fresh and after each of four stages
What this does not show: One batch cured by one method. The paper gives the vanillin content of the cured bean as 2.97 per cent in its results and 2.69 per cent in its conclusions. The beans were freeze-dried before analysis, so the percentages are of dry matter, not of the bean as sold.
Measured on the spice
Curing · Depends on conditions Vanillin, glucovanillin, enzyme activity
Comparing pods left to senesce, pods frozen and thawed, and pods cured traditionally, the authors found that traditionally cured beans reached only a medium yield of glucovanillin hydrolysis, under 50 per cent, with no measurable β-glucosidase activity and only partial breakdown of cell structure. They conclude that hydrolysis is governed by the breakdown of the compartments that keep enzyme and glucoside apart, that the level of β-glucosidase activity is not the limiting factor, and that where the compartments break down completely hydrolysis runs to completion even though most of the enzyme activity has been lost. Enzyme level, on their account, affects only the speed.
Conditions: Madagascan green pods ripened at 30 °C until black, frozen at −18 °C and thawed, or traditionally cured
What this does not show: Read in the abstract only, and some figures in the indexed abstract are garbled, so only its unambiguous statements are used. One batch of Madagascan pods.
Measured on the spice
Curing · Converts Vanillin, glucovanillin, other glucosides of shikimate-derived volatiles
Through ninety days of traditional curing in Mexico, 23 odour-active compounds were followed in both free and bound form. Fifteen were derived from the shikimate pathway and thirteen of those were present as glucosides. The glucosides did not behave alike: most of the glucovanillin was hydrolysed in the first stages of curing, others were released only in the later stages, and some were still partly or wholly bound after ninety days. The authors read the pattern as evidence that the hydrolysis is enzymatic and not simply chemical, and note that the freed compounds go on to be converted into one another, changing the aroma profile further.
Conditions: 90 days · Traditional curing in Mexico; free and glucosidically bound volatiles followed
What this does not show: Read in the abstract only, which gives no concentrations. One curing run in one region.
Measured on the spice
Curing · Converts Vanillin, glucovanillin, enzyme activity
A study of curing beans found that glucovanillin moves from the inner part of the bean towards the outside during curing and is hydrolysed as it goes, with enzymatic hydrolysis taking place at the surface. Transcripts of a β-glucosidase gene from colonising microorganisms were detected, and the colonisers belonged mainly to the genus Bacillus. In culture, the isolates consumed glucovanillin as their only carbon source within 24 h, and vanillin was the main volatile produced. The authors conclude that Bacillus colonising the bean produce β-glucosidase that takes part in glucovanillin hydrolysis.
Conditions: Isolates from curing beans grown in culture with glucovanillin as the only carbon source
What this does not show: Read in the abstract only. The isolates hydrolysed glucovanillin in culture; how much of the vanillin in a cured bean they account for was inferred and not measured.
Measured on the spice
Curing · Depends on conditions Vanillin, glucovanillin
Pods killed in four different ways and then cured alike ended with different amounts of vanillin. Freezing gave the most, 1.89 per cent of dry tissue, followed by sonication at 1.56 per cent, hot water at 1.33 per cent and microwave at 1.14 per cent. Glucovanillin stood at about 1.3 per cent after freezing, sonication and hot water but at 3.49 per cent after the microwave treatment, so the microwave-killed pods had released the least of their precursor. The authors relate the result for freezing to mechanical rupture of cell walls and organelles.
Conditions: Hot water at 80 °C; freezing at −10 °C; sonication at 60 °C; microwave at 100 W · Three 10 s dips; 24 h; 3 min; 2.5 min; then 30 days of sunning and sweating · Papantla pods, disinfected, wounded and sonicated after killing; conditioned for one week
What this does not show: A laboratory experiment with unusual additions: the pods were wounded and sonicated after killing and conditioned for a week instead of months. Twenty-eight pods per treatment from one harvest. It ranks four treatments in that design and does not show that frozen pods make better vanilla.
Measured on the spice
Curing · Increases Vanillin, enzyme activity
Applying microwaves or ultrasound at the killing stage was reported to raise vanillin yield significantly and to reduce curing time to 20 days. Pods killed by ultrasound and given a further sonication at 38 °C yielded more than twice the vanillin of the control, but when that further sonication ran to 15 min, inactivation of β-glucosidase lowered the final yield. No significant correlation was found between β-glucosidase activity and vanillin across the treatments.
Conditions: Curing completed in 20 days · Microwave or ultrasound at the killing stage, with a further sonication afterwards
What this does not show: Read in the abstract and conclusions only, which give no vanillin contents. An experimental procedure, and the study did not assess the aroma of the product beyond vanillin.
Measured on the spice
Curing
Freshly picked cardamom capsules are described as being washed and trimmed of their stalks, then dried from about 75 per cent moisture at harvest to 13 per cent for safe storage. Green capsules are usually flue-cured in special curing rooms, which the handbook says arrests the development of the fruit and fixes the green colour. Sun-drying is also common, sometimes followed by bleaching in sulphur fumes. The trade grades that result are named for appearance and not origin: whole green cardamom (flue-cured), whole bleached cardamom (sun-dried and bleached), whole straw-coloured cardamom (sun-dried), and decorticated seeds, which it attributes to poor processing.
Conditions: in air · Moisture reduced from about 75 per cent at harvest to 13 per cent for storage
What this does not show: A handbook description from the 1990s with no curing temperatures or times. It reports the reason given for flue-curing and does not test it.
Documented practice
Curing
To develop the yellow colour and the characteristic aroma, the cleaned rhizomes are described as being cooked in boiling water for an hour under slightly alkaline conditions and then dried in the sun for six to eight days; hot-air dryers are also used. The dried rhizomes are polished to smooth the surface and slightly improve the colour, either in a hand-turned drum of galvanised iron or in other equipment, and a small quantity of turmeric powder sprinkled in during polishing is said to give the product a good appearance.
Conditions: in water · Boiling water · Boiling for 1 h; sun-drying for 6 to 8 days · pH Slightly alkaline
What this does not show: A brief handbook description. Boiling times in the research literature read for this profile are much shorter, of the order of 10 to 25 min under steam, so the hour given here should be read as one account of one practice.
Documented practice
Smoking · Forms 96 volatile compounds identified; none named in the abstract, volatile oil
Following the volatile fraction of peppers through the traditional oak-smoke drying of La Vera, the authors identified 96 compounds, 55 of which differed significantly between days of the process. About 40 per cent of the aromatic potential of the finished product belonged to compounds that appeared during drying, originating either from the wood smoke or from reactions typical of dehydrated products.
Conditions: in smoke · Traditional slow drying of peppers in La Vera drying barns heated by oak-wood fires
What this does not show: Read in the abstract only, which names no compound and does not separate smoke-derived volatiles from those formed by drying itself.
Measured on the spice
Smoking · Retains total carotenoids, colour
During the slow traditional drying of La Vera, the carotenoid content of the peppers passed through phases of decrease and increase that tracked the conditions in the dryer: the milder regimes gave a regular course and the more severe ones an irregular one. In every case the dried fruits ended with carotenoid values similar to those they began with, and no group of pigments was preferentially destroyed or formed.
Conditions: in smoke · Slow drying at mild temperatures in La Vera, with temperature and time monitored throughout
What this does not show: Read in the abstract only, which gives no temperatures, times or contents. It concerns the whole dried fruit before milling; colour loss in the ground spice during storage is a separate matter.
Measured on the spice
Smoking · Depends on conditions benzo(a)pyrene, chrysene, benzo(b)fluoranthene, benzo(a)anthracene, colour, moisture
Across four seasons of smoke-drying for Pimentón de La Vera, the summed content of four polycyclic aromatic hydrocarbons in the dried peppers ranged from 277 to 1208 µg/kg between seasons and from 432 to 932 µg/kg between types of dryer. A modified dryer in which the firewood burned in a closed chamber and the air was moved by a fan lowered the contamination while keeping quality; its peppers had the highest extractable colour, 133 ASTA units. Fresh peppers varied from 69.4 to 81.4 per cent moisture between seasons, and the final moisture did not differ by dryer type.
Conditions: in smoke · A traditional smoke dryer compared with two modified designs over four seasons
What this does not show: Read in the abstract only. The figures are for dried peppers from the dryers studied, not for paprika on sale, and the abstract does not compare them with any legal limit.
Measured on the spice
Fermenting
To make white pepper, the fruit spikes are described as being lightly crushed, put into gunny sacks and soaked for seven to ten days, preferably in slow-running water, until the flesh of the berry disintegrates. The peppercorns are then trampled loose, washed and sieved, and dried in the sun for three to four days, during which the white to cream colour develops. The handbook adds that where stagnant water has been used the dried peppercorns turn grey and give off a musty odour. White pepper weighs about 26 per cent of the fresh fruit, against about 33 per cent for black.
Conditions: in water · Soaking for 7 to 10 days; sun-drying for 3 to 4 days · Preferably in slow-running water; final moisture usually 10 to 14 per cent
What this does not show: A description of practice in Sarawak and Indonesia in the 1990s. It gives no water temperature and names no odour compound.
Documented practice
Fermenting · Forms 3-methylindole (skatole), 4-methylphenol, 3-methylphenol, butanoic acid
In white pepper sampled from a retting batch at a Thai production plant, the compounds responsible for the faecal off-odour of some white pepper were measured by stable isotope dilution. 3-Methylindole, 4-methylphenol and butanoic acid were shown to be formed biochemically during retting, which the authors identify as the crucial step for off-odour formation in white pepper processing. In model fermentations, white pepper with no substantial amounts of these odorants was produced from ripe berries by a short fermentation under water with frequent changes of the water, and its overall aroma was judged superior to pepper made by the traditional procedure.
Conditions: in water · Samples taken directly from a retting batch at a production plant in Thailand; model fermentations under different regimes
What it means in practice:The farmyard note in some white pepper is a product of how long and in what water the berries were retted, not a property of white pepper as such.
What this does not show: Read in the abstract only, which gives no concentrations or retting times. One plant in Thailand and a set of model fermentations.
Measured on the spice
Fermenting · Decreases pectin, cellulose, hemicellulose, galacturonic acid, enzyme activity, texture
When abraded pepper berries were retted for 60 h, the fruit wall lost 66.38 per cent of its pectin, 43.78 per cent of its cellulose and 32.76 per cent of its hemicellulose, pectinase activity rose from 3.36 to 8.74 mg/h/g, and the share of berries peeled climbed from 5.2 per cent to 99.67 per cent. Sequencing showed a succession of microorganisms: Prevotella rose from 0.87 per cent to 75.45 per cent of bacterial reads, with Lactococcus, Selenomonas, Streptococcus, Weissella and Enterobacter also prominent, while among fungi Candida rose from 45 per cent to about 90 per cent. Galacturonic acid, glucose and xylose accumulated in the fruit wall. In a test with purified enzymes, pectinase accelerated peeling while cellulase and hemicellulase had little effect, and polygalacturonase alone gave complete peeling within 8 h.
Conditions: in water · Room temperature · 60 h · pH 5.50 at the start, 5.92 at 36 h, 5.50 at 60 h · Berries abraded for 3 min in a peeling machine, then soaked 1:4 in citric acid buffer
What this does not show: A buffered 60 h soak after mechanical abrasion, not the week or more of traditional retting, so the organisms and the time course may differ. Relative abundance from sequencing is not a count. The study measured neither aroma nor off-odorants.
Measured on the spice
Fermenting · Retains Piperine, 3-methylindole (skatole), volatile oil
Of 45 bacterial isolates taken from black pepper, seven removed the fruit wall of fresh berries almost completely (98 to 100 per cent) and of dried black pepper in part (over 60 per cent) within five days of immersion. They were identified by 16S rRNA sequencing as strains of Bacillus subtilis, Bacillus licheniformis, Acinetobacter baumannii, Klebsiella pneumoniae and Microbacterium barkeri, and were found to secrete cellulase, pectinase, amylase, protease and xylanase. The white pepper obtained was reported free of the off-odour compound skatole, with oleoresin, piperine and essential oil within the acceptable range and their constituents unaffected.
Conditions: in water · Within 5 days · Fresh ripe berries or dried black pepper immersed in a suspension of selected bacterial isolates
What this does not show: Read in the abstract only, which gives no piperine or oil figures. Work by the developers of the process, whose strains are patent deposits; two of the species named include strains that cause disease, and the abstract does not discuss that.
Measured on the spice
Fermenting · Depends on conditions 3-carene, limonene, sabinene, β-caryophyllene, α-copaene, volatile oil
White pepper made by mechanical peeling alone carried more headspace volatiles than pepper peeled mechanically after steaming or pepper retted in water and rubbed by hand. Among the retted samples, seven days of immersion gave more monoterpenes and sesquiterpenes than five or ten days. Twenty volatiles were found in every sample, thirteen monoterpenes and seven sesquiterpenes; 3-carene, limonene and sabinene were the most abundant monoterpenes and β-caryophyllene the most abundant sesquiterpene. By relative odour activity, 3-carene accounted for at least 55 per cent of the calculated aroma in each sample and limonene for about 21 per cent. α-Copaene, which the authors associate with a woody note, was highest after five days of immersion and fell sharply with longer soaking.
Conditions: Steaming at 100 °C; drying at 65 °C · Immersion for 5, 7 or 10 days; steaming for 15 to 25 min; drying for 7 h · Mechanical peeling at 30, 45 or 60 r/min compared with immersion followed by hand rubbing
What this does not show: Headspace measurements on 40 g lots, compared within one study; the absolute figures are far above any volatile-oil content and are not used here. Piperine and the off-odorants of retting were not measured, and no sensory panel was used.
Measured on the spice
Decontamination · Retains Piperine, total phenolics, microbial load, colour, volatile oil
Radio-frequency heating of inoculated black peppercorns for 2.5 min reduced Salmonella by 5.31 log CFU/g and the surrogate Enterococcus faecium by 5.26 log CFU/g across the whole tray. Colour, piperine content, total phenolics, radical-scavenging activity and most of the volatile compounds in the treated peppercorns were not significantly different from the untreated control. The cold spot of the load was at the centre of the top surface.
Conditions: 2.5 min of radio-frequency heating · Peppercorns conditioned to 12.7 per cent moisture and water activity 0.60
What this does not show: Read in the abstract only. “Most” volatile compounds leaves some that did change, and the abstract does not name them. A laboratory unit and one moisture content; the result depends on the peppercorns having been conditioned to that moisture.
Measured on the spice
Decontamination · Retains microbial load, colour
Radio-frequency heating for 50 s reduced inoculated Salmonella Typhimurium and Escherichia coli O157:H7 on whole and ground black pepper by 2.80 to 4.29 log CFU/g, and 40 s on red pepper of three particle sizes reduced them by 3.38 log CFU/g to more than 5 log, below the limit of detection. The colour of the samples was not affected.
Conditions: 50 s for black pepper; 40 s for red pepper · Whole and ground black pepper; red pepper in three mesh fractions · 27.12 MHz parallel-plate radio-frequency heater
What this does not show: Read in the abstract only. Colour was the only quality measure reported there; volatile oil and pungency were not. Reductions varied with particle size.
Measured on the spice
Decontamination · Retains Capsaicin, Capsanthin, hexanoic acid, tetramethylpyrazine, 1,3-di-tert-butylbenzene, microbial load, colour, pungency
Gamma irradiation of vacuum-packed Korean red pepper powder at 7 kGy reduced mesophilic bacteria and fungi effectively. Pungency was unchanged, by capsaicinoid content and by Scoville score, and the red colour did not differ significantly from the control by capsanthin content, ASTA units or Hunter values. A panel found no significant difference in pungent odour or off-odour. Instruments could nonetheless tell the doses apart: the headspace profiles separated at 0, 3, 5 and 7 kGy, with hexanoic acid and tetramethylpyrazine disappearing and 1,3-di-tert-butylbenzene appearing, a compound the authors trace to the irradiated packaging film migrating into the powder.
Conditions: Up to 7 kGy of gamma irradiation; powder vacuum-packed in a polyethylene/polypropylene bag
What this does not show: Read in the abstract only. A later study by another group reported that most panellists did detect an off-flavour in irradiated red pepper powder, so the sensory result is not settled. The packaging finding belongs to that film.
Measured on the spice
Decontamination · Retains Capsaicin, Capsanthin, microbial load, colour, pungency
Red pepper powder irradiated with gamma rays, electron beams or X-rays lost total aerobic microbes in proportion to the dose, and 6 kGy from any of the three sources reduced the population effectively. None of the three changed the capsaicinoid content, and neither capsanthin content nor Hunter colour values differed significantly from the control. A sensory panel found no significant difference in pungent odour or colour, but most panellists detected an off-flavour in the irradiated samples from every source.
Conditions: Gamma rays, electron beams and X-rays at doses up to 10 kGy
What this does not show: Read in the abstract only, which does not describe the off-flavour or the dose at which it appeared. An earlier study found no significant difference in off-odour at up to 7 kGy; the two used different panels and doses.
Measured on the spice
Decontamination · Depends on conditions Capsaicin, total carotenoids, N-methylpyrrole, dihydroactinidiolide, microbial load, colour
Electron-beam irradiation at 10 kGy left bacteria, yeasts and moulds almost undetectable in three paprika varieties. At 25 kGy the total carotenoid content had fallen by 16.91, 22.09 and 24.76 per cent in the three varieties. Capsaicin content did not change significantly with dose in two of them. New volatile compounds, N-methylpyrrole and dihydroactinidiolide, increased as the dose rose. The authors conclude that treatment up to 10 kGy was effective while preserving the properties they measured.
Conditions: Electron-beam irradiation at doses up to 25 kGy on three paprika varieties
What this does not show: Read in the abstract only. The carotenoid losses quoted are at 25 kGy, well above the dose the authors recommend; the abstract does not give the loss at 10 kGy.
Measured on the spice
Decontamination · Depends on conditions Capsaicin, total carotenoids, phenolic acids, microbial load, colour
In a traditional Himalayan paprika, gamma irradiation at 3 kGy gave a two-log reduction in bacterial count and a three-log reduction in yeasts and moulds, and in samples irradiated at 6 and 9 kGy no microbial growth was observed through nine months of storage. Measured capsaicinoids and phenolic acids increased significantly with irradiation, while carotenoids decreased significantly.
Conditions: Gamma irradiation at 3, 6 and 9 kGy, followed by storage under ambient conditions
What this does not show: Read in the abstract only, which gives no figures for the changes on irradiation itself. The abstract does not explain the apparent rise in capsaicinoids after irradiation, which should not be read as new capsaicinoid being formed.
Measured on the spice
Decontamination · Decreases Piperine, colour, microbial load
Ground black pepper that had been steamed came out darker than untreated pepper, and its piperine fell considerably, both on treatment and over the six months of storage that followed. Irradiated pepper from the same study lost more of its microbial load and showed minimal change in composition, colour or sensory quality. Keeping the pepper at 4 °C slowed the loss of piperine.
Conditions: in steam · Followed through 6 months of storage after treatment · Steam treatment compared with irradiation; stored at refrigerator and at room temperature
What this does not show: Read in the abstract only, which gives neither the steam conditions nor any figures: “considerable” is the authors’ word. One study on pepper that was already ground, which exposes far more surface to steam than a whole peppercorn does.
Measured on the spice
Decontamination · Retains volatile oil, moisture, microbial load
Whole black peppercorns given a few seconds of steam and then put abruptly under vacuum lost a thousandfold of their bacteria — a three-log reduction after 10 seconds at 125 °C or 20 seconds at 120 °C — while the authors found the changes in moisture and volatile oil content acceptable and could detect no change in the composition of the oil. Ten, fifteen and twenty seconds of steam gave almost the same reduction, which the authors attribute to the sudden evacuation acting mechanically on the surface as well as to the heat.
Conditions: in steam · Steam at 100 to 130 °C · 5 to 20 s, followed by rapid evacuation · Whole peppercorns carrying their natural load of 10 to 60 million bacteria per gram
What this does not show: Read in the abstract only. “Acceptable” is the authors’ judgement and no figure for the oil is given. The count is of all aerobic bacteria, not of Salmonella, and a three-log reduction is well short of what a validated pathogen-reduction step is expected to deliver.
Measured on the spice
Decontamination · Depends on conditions volatile oil, microbial load
Two studies of steamed black pepper, set side by side in the United States regulator’s review of spice treatments, reach opposite conclusions about its aroma. Tasters in 1942 judged ground pepper autoclaved for 5 to 15 minutes at 108 to 121 °C to be minimally changed. A 2010 study using gas chromatography with a human assessor at the detector found “a remarkable decrease in the overall aroma” after three minutes of dry steam at 130 °C. The review points to the method as the difference: the earlier work used unaided tasting and no chemical analysis. It adds that steaming puts moisture into a spice, which can itself harm quality, and that gentler steam processes built on controlled condensation were designed to reduce the sensory cost.
Conditions: in steam · 108 to 121 °C under pressure in one study; dry steam at 130 °C in another · 5 to 15 min in one study; 3 min in the other
What this does not show: Known here through the review’s account of the two studies, neither of which was read. The treatments differ in temperature, time and kind of steam as well as in how aroma was judged, so the comparison shows that the question is unsettled, not which answer is right.
Review of studies
Decontamination · Decreases pyrrolizidine alkaloids and their N-oxides, volatile oil, microbial load
Steam sterilisation and gamma irradiation were the two treatments that did most against the microbes on dried oregano, cutting total aerobic bacteria by 0.87 to 2.15 log and taking yeasts, moulds and Enterobacteriaceae below the level of detection. Steam also changed the herb’s volatile compounds significantly: the levels of the major components fell and some compounds appeared that the untreated oregano did not hold, as they did after ultraviolet light and ozone. The pyrrolizidine alkaloids measured in the oregano changed form under steam, from their N-oxides to the parent alkaloids; of the four treatments only ozone lowered them.
Conditions: in steam · Steam sterilisation compared with gamma irradiation, ultraviolet light and ozone on dried oregano
What this does not show: Read in the abstract only, which names none of the volatile compounds, gives no size for their loss and no steam conditions, and does not report whether irradiation changed the volatiles. A change in a volatile profile is not a tasting result.
Measured on the spice
Decontamination · Depends on conditions linoleic acid, DL-malic acid, flazin, microbial load
Untargeted metabolomics separated heat-sterilised paprika from untreated paprika with perfect prediction in the authors’ model, on the strength of 19 marker compounds that included fatty acids and amino acids. Sterilisation reduced fatty acids such as linoleic acid and increased others, among them malic acid and flazin. The authors note that heat sterilisation, free of chemicals and radiation, is becoming the expected treatment on the European market.
Conditions: Heat sterilisation as applied commercially, compared with untreated paprika by untargeted metabolomics
What this does not show: Read in the abstract only, which does not give the sterilisation conditions, does not say whether steam was used, and reports no colour, aroma or microbial data. It shows that the treatment leaves a chemical trace, not that the spice is worse for it.
Measured on the spice
Decontamination · Decreases microbial load, water activity
Naturally contaminated paprika powder, moistened to a water activity of 0.88 and then brought to 98 °C and held there for 20 min, lost 4.8 log units of mesophilic bacteria when the heating-up was done by microwave and 3.8 log units when it was done by infrared. The two heating methods produced different temperature and moisture patterns within the powder during heating-up, which the authors consider the likely reason for the difference.
Conditions: 98 °C · Heating-up in 1.5 min by microwave or 3.7 min by infrared, then held for 20 min · Naturally contaminated powder adjusted to water activity 0.88
What this does not show: Read in the abstract and conclusions only. The powder had to be moistened first, and the parts read report nothing on what the treatment did to colour or aroma, which is the reason such alternatives are sought.
Measured on the spice
Decontamination · Decreases red pigment fraction, yellow pigment fraction, brown pigments, microbial load, colour, pungency, water activity
Combined microwave-infrared heating of paprika reduced inoculated Salmonella Typhimurium by 7.389 log and Aspergillus flavus by 6.182 log. During heating the red pigments deteriorated more than the yellow, and the change of colour was attributed to a large increase in brown pigments. The measured pungency of the dried paprika increased, which the authors relate to the reduction in moisture, inactivation of peroxidase and the short duration of heating.
Conditions: Short, intensive combined microwave-infrared heating
What this does not show: Read in the abstract only, which gives no temperatures, times or colour values and names the pigments only as red and yellow fractions.
Measured on the spice
Decontamination · Depends on conditions Carvacrol, Thymol, microbial load, water activity, colour, volatile oil
Infrared heating of moistened oregano reduced inoculated Bacillus cereus spores by 5.6 log units after 10 min at 90 °C; at 100 °C for the same time the reduction was lower, 4.7 log units, which the authors link to the water activity having fallen to 0.76 during treatment. The green colour was only slightly affected. The composition of the headspace volatiles was clearly altered, but carvacrol and thymol, two of the key aroma compounds, were only slightly affected compared with the other compounds studied.
Conditions: 90 and 100 °C · Holding times of 2 and 10 min · Oregano conditioned to water activity 0.88, in a closed infrared heating unit
What this does not show: Read in the abstract only. The oregano was moistened before treatment and would have to be dried again. Which volatiles were lost is not stated in the abstract.
Measured on the spice
Decontamination · Depends on conditions Thymol, γ-Terpinene, p-Cymene, Carvacrol, monoterpene hydrocarbons, oxygenated monoterpenes, microbial load, volatile oil
Sicilian oregano, whose oil consisted mainly of thymol and γ-terpinene with p-cymene, α-terpinene and carvacrol, showed a changed oil profile after gamma irradiation: fewer monoterpene hydrocarbons and more oxygenated monoterpenes. Total bacterial and fungal counts fell below 10 cfu/g at the lower dose, 5 kGy. A sensory panel found significant differences between irradiated and untreated oregano for every descriptor except bitter, pungent, astringent and hay.
Conditions: Gamma irradiation at 5 and 10 kGy on three cultivated Sicilian oregano samples
What this does not show: Read in the abstract only, which gives no percentages and does not say in which direction the sensory descriptors moved.
Measured on the spice
Decontamination · Depends on conditions monoterpenes, oxygenated compounds, microbial load, volatile oil, colour
Black pepper, Cumin, Thyme, Rosemary
Ground thyme, rosemary, black pepper and cumin were irradiated in packs filled either with air or with nitrogen. After 12 kGy no microbial load was detectable in any sample. Irradiation changed the colour of rosemary and black pepper significantly, and the discolouration of black pepper was smaller under nitrogen. The essential oil yield of irradiated black pepper and cumin was lower in air than under nitrogen. In general irradiation decreased monoterpenes and increased oxygenated compounds, and the effect was smaller under nitrogen. The authors conclude that spices should be irradiated in an oxygen-free atmosphere.
Conditions: Gamma irradiation at 7, 12 and 17 kGy; packed in air or in 100 per cent nitrogen
What it means in practice:The damage irradiation does to a spice’s oil appears to be largely oxidative, since removing the oxygen from the pack reduced it.
What this does not show: Read in the abstract only, which gives no oil yields.
Measured on the spice
Decontamination · Retains Cuminaldehyde, γ-Terpinene, p-Cymene, γ-terpinen-7-al, β-pinene, microbial load, volatile oil, colour
Cumin seed passed through an induction heater at 155 °C for 60 s showed its aerobic plate count fall from 6.21 to 2.97 on the logarithmic scale, and at 155 °C for 45 s moulds and yeasts fell by about 3.2 and coliforms by 3.6. No statistically significant difference in essential oil content was found between treated and control seed, and the oil remained within the composition of the ISO standard, with γ-terpinen-7-al (38.98 per cent), cuminaldehyde (20.75 per cent), γ-terpinene (18.81 per cent), β-pinene (13.66 per cent) and p-cymene (6.2 per cent) as the main constituents. Colour did change, increasingly with temperature and time.
Conditions: 115, 135 and 155 °C · 45, 60 and 75 s · Continuous non-contact induction heater with a screw conveyor, laboratory scale
What this does not show: Read in the abstract and conclusions only. A self-built laboratory unit; the authors themselves call for work on uniformity of heating and on how the treated seed keeps.
Measured on the spice
Decontamination · Retains microbial load, colour
On red pepper powder inoculated with Bacillus cereus, mild heat at 60 °C alone gave reductions of 0.23 to 1.43 log CFU/g and plasma alone 0.12 to 0.96 log CFU/g. The two together gave reductions of 6 log CFU/g or more, the largest synergy coming from 20 min of heat with 5 to 15 min of plasma. Hunter L, a and b colour values and pH after the combined treatment were not significantly different from those of untreated powder.
Conditions: Mild heat at 60 °C · 5 to 20 min of heat and 5 to 20 min of plasma · Dielectric barrier discharge plasma; powder inoculated with three strains of Bacillus cereus
What this does not show: Read in the abstract and conclusions only. Colour and pH were the only quality measures reported there; volatile compounds and capsaicinoids were not. An inoculated laboratory test, not a validated process.
Measured on the spice
Decontamination · Decreases microbial load
In a study of three commercial Spanish paprikas published in 1986, both ethylene oxide and gamma irradiation reduced bacterial levels to acceptable ones, and gamma irradiation was found substantially more effective. Bacterial growth afterwards was greater without cold storage, regardless of how long the paprika was kept.
Conditions: Three commercial Spanish paprikas treated with ethylene oxide or gamma irradiation, then stored with and without refrigeration
What this does not show: Read in the abstract only, which is a brief summary without figures, doses or any quality measure, and it says nothing about residues.
Measured on the spice
Decontamination · Decreases aflatoxins, microbial load, volatile oil
Nine powdered sun-dried herbs and spices carried fungi dominated by Aspergillus, Penicillium, Fusarium and Rhizopus. After 280 min of exposure to ozone at 3 ppm, the fungal count had fallen by 96.39 to 98.26 per cent. The treatment had a cost: the total volume of essential oil fell by 26.67 per cent in peppermint and by 57.14 per cent in chamomile. The authors conclude that ozone can sanitise herbs but that its effect on their active constituents has to be weighed before it is recommended for industrial use.
Conditions: Exposure for up to 280 min · Ozone gas at 3 ppm on nine powdered sun-dried herbs and spices, including peppermint and chamomile
What this does not show: Read in the abstract only. Oil losses are reported for two of the nine materials; the abstract does not give them for the others. One ozone concentration.
Measured on the spice
Packaging · Depends on conditions total phenolics, volatile oil, microbial load, antioxidant capacity, colour
Thyme and black pepper were packed in air or in nitrogen, irradiated and stored for six months. Irradiation under nitrogen raised the essential oil yield of the samples at the start of storage. A dose of 14 kGy brought total bacteria and yeasts and moulds below 1 log cfu/g, from initial levels of 7.7 and 5.2 log. Over the six months the essential oil yield of thyme declined, as did its radical-scavenging and antimicrobial activity, and one measure of antioxidant activity fell in black pepper packed in air. The authors conclude that irradiating under nitrogen maintained or improved the properties they measured without compromising sensory or microbial quality.
Conditions: 6 months · Packed in air or 100 per cent nitrogen, gamma-irradiated at 0, 6 or 14 kGy, then stored
What this does not show: Read in the abstract only, which gives no oil yields and does not say how much of the decline in thyme was slowed by the nitrogen pack. Storage temperature is not stated there.
Measured on the spice
Packaging · Decreases Capsaicin, pungency, colour
Red chilli powder sealed in pouches and held at 40 °C for six months lost capsaicinoid content in every package, and the size of the loss depended on the film. It was greatest in polyethylene, 25.9 per cent, and least in a starch-based film plasticised with sorbitol, 15.7 per cent. The loss of extractable colour, measured by the ASTA method, followed the same order.
Conditions: 40 °C · 6 months · Heat-sealed starch-based film pouches compared with polyethylene
What this does not show: Read in the abstract only. An experimental film against one commercial polyethylene, at a temperature well above ordinary storage; capsaicinoids were measured by spectrophotometry, and the barrier properties of the films are not given there.
Measured on the spice
Packaging · Depends on conditions shelf life, moisture, water activity
Four paper-and-plastic laminate packs were compared for turmeric and nutmeg powder under accelerated conditions of 38 °C and 90 per cent relative humidity. The two packs with a barrier layer of aluminium foil or metallised polyester film showed superior barrier properties to the two without. For the pack with the metallised layer, the authors report a shelf-life extension of 480 days for turmeric and 390 days for nutmeg.
Conditions: 38 °C · Accelerated conditions at 90 per cent relative humidity; four paper-based laminate packs
What this does not show: Read in the abstract only. The day counts are the authors’ estimates for those packs under that test, with the criterion for the end of shelf life not stated there; they are not keeping times for turmeric or nutmeg in general.
Measured on the spice
Packaging · Depends on conditions Hydroxy-α-sanshool, total polyphenols, total flavonoids, volatile oil, antioxidant capacity
Screening single storage factors for dried Sichuan pepper, the authors found that 5 °C and an oxygen-free atmosphere significantly slowed the loss of polyphenols, flavonoids and flavour compounds, and that yellow LED light, of the four colours tried, best preserved hydroxy-α-sanshool. Combining nitrogen, yellow light and cold storage over 60 days reduced the losses of polyphenols and flavonoids by 46.88 and 57.00 per cent compared with the control and held hydroxy-α-sanshool at 19.04 mg/g.
Conditions: 5, 10, 20 and 40 °C screened; cold storage in the combined treatment · 60 days · Oxygen at 0 to 40 per cent; white, red, blue and yellow LED light; nitrogen, yellow LED and cold combined
What this does not show: Read in the abstract and conclusions only. The sanshool content of the control at 60 days is not given there, and the abstract’s percentage for the reduced loss of sanshool is not coherent as printed, so it is not repeated. A 60-day laboratory test.
Measured on the spice
Packaging
Packing methods for cardamom are described as resting on three things: controlling the moisture content, avoiding physical damage and avoiding excessive heat. For green cardamom, light must be excluded as well, and the handbook says it should be packed in wooden boxes or tins lined with heavy-gauge black polythene, metal foil or waterproof paper. It adds that grinding takes place almost entirely in the consuming countries, and that the whole spice loses essential oil by evaporation, whereas the distilled oil deteriorates through chemical change.
Conditions: Wooden boxes or tins lined with heavy-gauge black polythene, metal foil or waterproof paper
What this does not show: A handbook description from the 1990s. It states that light must be excluded to keep the green colour but cites no measurement of colour loss.
Documented practice
Storage · Converts Piperine, Isopiperine, Chavicine, Isochavicine
Light converts piperine into its three geometric isomers: isopiperine, chavicine and isochavicine. Under fluorescent light, sunlight and ultraviolet the conversion increased with the intensity of the light and the time of exposure, then levelled off at a steady mixture. In four commercial ground black peppers the three isomers were all present, but in small amounts beside piperine: on the scale the authors used, piperine measured about 10 to 12, isochavicine 0.37 to 0.42, isopiperine 0.15 to 0.23 and chavicine 0.01 to 0.07.
Conditions: Fluorescent light, sunlight and 254 nm ultraviolet at varying intensity and exposure time
What it means in practice:The isomerisation is real, but in the ground pepper these authors bought it had not gone far: piperine still greatly outweighed its isomers. Light is one route by which pepper can lose pungency, not proof that a given jar has.
What this does not show: Read in the abstract only. The kinetics were measured on the compounds under laboratory lamps, the abstract gives no rates, and it does not report the pungency of the isomers or the storage history of the four products.
Measured on the spice
Storage · Decreases Crocin, Picrocrocin, crocetin esters trans-4-GG, trans-3-Gg, trans-2-G and cis-4-GG, colour
Saffron from a single farm, harvested in different years and kept in zip-lock bags at room temperature, had lost 52.2 per cent of its crocetin esters and 54.3 per cent of its picrocrocin after the first year. The rate of loss then slowed over the following years. The individual pigments did not move together: the two main trans esters fell every year, while two minor ones fell, rose and fell again. On the basis of these data the authors suggest that saffron of this origin should not be kept for more than two years.
Conditions: Room temperature, in a cool and dry place · Samples from 1 to 15 years old · Zip-lock bags; all samples from one farm and dried alike at 110 °C for 6 min
What this does not show: The samples are different harvests analysed at one time, not one lot followed through the years, so differences between seasons are mixed in with the effect of storage. A zip-lock bag at uncontrolled humidity is a poor package; better-protected saffron may keep differently.
Measured on the spice
Storage · Depends on conditions Safranal, 4-hydroxy-2,6,6-trimethyl-1-cyclohexene-1-carboxaldehyde (HTCC), 3,5,5-trimethyl-2-cyclohexen-1-one
Across 73 saffron samples in three age groups, safranal remained the main volatile at 30.14 to 43.94 per cent of the total, but the profile changed with age. The major compounds differed significantly between saffron less than a year old and saffron stored for three to four or eight to nine years. Saffron under a year old carried more of the notes described as saffron, flower and spicy; the older saffrons carried volatiles with vegetal, caramel and citrus notes.
Conditions: Under 1 year, 3 to 4 years, and 8 to 9 years · 73 samples in three age groups
What this does not show: Read in the abstract only. The samples in the three groups are different saffrons, and the abstract does not describe how they had been stored.
Measured on the spice
Storage · Depends on conditions Crocin, Picrocrocin, Safranal, β-isophorone, 4-hydroxy-3,5,5-trimethylcyclohex-2-enone, colour
Comparing freshly dried saffron with saffron stored for two years, the authors found that the fresh samples held more of the crocins, of picrocrocin and of two minor volatiles, while the stored samples held more safranal. They conclude that during storage the intensity of saffron’s colour falls while its aroma compound increases, the two moving in opposite directions.
Conditions: Freshly dried against two years of storage
What it means in practice:Old saffron can smell strongly of safranal and still have lost much of its colouring power, so smell alone is a poor guide to its condition.
What this does not show: Read in the abstract only, which gives relative levels and no figures, and does not state the storage conditions.
Measured on the spice
Storage · Depends on conditions Vanillin, 2-acetylpyrrole, 5-hydroxymethylfurfural, nonanal, 3,5-octadien-2-one, colour
Cured vanilla beans stored at four temperatures diverged with time. Vanillin was highest in beans held at −20 °C for six months, with no perceptible change of colour. At 35 °C, products of lipid breakdown, enzymatic oxidation and the Maillard reaction, among them 2-acetylpyrrole and 5-hydroxymethylfurfural, were detected after 18 months, the colour had changed perceptibly, and the odour profile no longer met the standard the authors applied. Beans kept at −20 or 4 °C stayed within its colour requirements. Nonanal and 3,5-octadien-2-one were put forward as indicators of oxidation.
Conditions: −20, 4, 25 and 35 °C · Up to 24 months · Cured beans from Taiwan, assessed against the ISO specification for vanilla
What this does not show: Read in the abstract and conclusions only. One origin and one lot; the packaging and humidity are not stated there, and freezing whole beans has consequences for texture that the study did not report.
Measured on the spice
Storage · Depends on conditions 3-methylindole (skatole), 4-methylphenol, 3-methylphenol, butanoic acid, α-pinene, volatile oil
When a freshly ground white pepper powder was stored for up to seven months, its typical pepper odour qualities decreased significantly and its faecal note increased. The concentrations of the off-odorants themselves, 3-methylindole, the methylphenols and the short-chain acids, hardly changed over that time. The authors therefore suggest that the off-note emerges because very volatile odorants such as α-pinene, which mask it in fresh powder, are lost during storage. In 50 commercial white peppers the same off-odorants were present at similar concentrations in most samples, although the strength of the off-note differed clearly.
Conditions: Up to 7 months · Freshly ground white pepper powder
What it means in practice:White pepper that smells clean when freshly ground can turn farmyard-like in the jar without anything new forming: the pleasant volatiles leave and the unpleasant ones stay.
What this does not show: Read in the abstract only. The masking explanation is the authors’ hypothesis. Storage conditions and packaging are not given there.
Measured on the spice
Storage · Retains total carotenoids, peroxides, colour, microbial load
Paprika stored at 4 °C and 70 per cent relative humidity, without any addition of antioxidants, kept its carotenoid content and colouring capacity: the course of the carotenoids showed that autoxidation took place only minimally. Peroxide values were very low, rising from about 1 to 3 milliequivalents per kilogram by the end of storage, and the microbial flora stayed at levels similar to those at the start. The authors conclude that controlled storage alone was enough to preserve the paprika.
Conditions: 4 °C · 70 per cent relative humidity, industrial controlled conditions, no antioxidant added
What this does not show: Read in the abstract only, which does not state how long the storage lasted or the ASTA values. Industrial cold storage; it does not describe paprika at room temperature.
Measured on the spice
Storage · Decreases total carotenoids, tocopherol, colour
During twelve months of storage in the dark, paprika made from conventional, organic and frost-damaged peppers lost 60.2, 99.7 and 79.3 ASTA units of colour respectively. Added tocopherol slowed carotenoid degradation in the dark by 28, 32 and 40 per cent. Under light the losses were faster and followed apparent zero-order kinetics: after one month at 2000 lux, supplemented paprika retained 1.14 to 1.56 times the colour of unsupplemented paprika, and the protection given by the antioxidant grew to 47 to 56 per cent at 6000 lux.
Conditions: 12 months in the dark; 1 month under light · Illumination at 2000, 4000 and 6000 lux; with and without added tocopherol
What it means in practice:Paprika loses colour in the dark as well as in the light; keeping it out of the light slows the loss and does not stop it.
What this does not show: Read in the abstract only. The starting ASTA values, the temperature and the packaging are not stated there, so the losses cannot be turned into percentages.
Measured on the spice
Storage · Decreases Capsaicin, Capsanthin, dihydrocapsaicin, capsorubin, zeaxanthin, β-carotene, β-cryptoxanthin, pungency, colour
In a traditional Himalayan paprika stored under ambient conditions, total capsaicinoids and phenolic acids decreased significantly with storage, and so did the carotenoids. In the samples irradiated at 9 kGy, dihydrocapsaicin fell by 23.3 per cent and capsaicin by 21.0 per cent. Among the pigments, capsorubin fell least, by 19.2 per cent, against 29.9 per cent for capsanthin, 28.5 per cent for zeaxanthin and 29.5 per cent each for β-carotene and β-cryptoxanthin.
Conditions: Up to 9 months · Ambient conditions; figures are for samples irradiated at 9 kGy
What it means in practice:In this paprika the pungent compounds were not indefinitely stable on the shelf: about a fifth was gone within the storage period, a smaller loss than that of the pigments but a real one.
What this does not show: Read in the abstract only. The percentages are given for the irradiated samples; those for the untreated control are not in the abstract, and neither are the packaging, temperature or humidity.
Measured on the spice
Storage · Depends on conditions moisture, water activity
Moisture sorption isotherms of an Ethiopian chilli showed that, at a given water activity, the equilibrium moisture content fell as temperature rose and as the fruit matured: green chilli held the most water, red the least and brown lay between. Desorption and adsorption curves did not coincide, so that a chilli drying down holds more water at a given humidity than one taking water up. The GAB and BET models described the green fruit and the Oswin model the brown and red. The net isosteric heat of sorption of green chilli reached 18 kJ/mol in adsorption and 20 kJ/mol in desorption and fell exponentially as moisture rose.
Conditions: Three temperatures · Relative humidity 10 to 92 per cent; Ethiopian variety Mareko Fana at green, brown and red maturity
What it means in practice:How much moisture a dried chilli holds in a given store depends on the chilli and on whether it is drying or re-wetting, so a single moisture figure does not define a safe condition for every lot.
What this does not show: Read in the abstract and conclusions only, which do not give the three temperatures or any equilibrium moisture values. One variety.
Measured on the spice
Storage · Forms aflatoxins B1, B2 and G2, penicillic acid, patulin, water activity, microbial load
When smoked dried peppers were inoculated with moulds able to produce toxins and held for 30 days at 20 °C, what formed depended on the humidity. Patulin was not detected under any condition. Penicillic acid was detected at 91 to 97 per cent relative humidity, and aflatoxins G2, B1 and B2 at 91 to 97 per cent, with the highest concentrations at 94 per cent. Nothing is reported as forming at 84 per cent. The authors conclude that the drying and storage of the peppers must be controlled up to the milling step to avoid rehydration.
Conditions: 20 °C · 30 days · Smoked dried peppers inoculated with toxigenic moulds and held at 84, 91, 94 and 97 per cent relative humidity
What this does not show: Read in the abstract only. An inoculation experiment with selected isolates at one temperature; it shows the humidity at which those moulds made toxin on that substrate, not a general threshold.
Measured on the spice
Storage · Decreases Curcumin, demethoxycurcumin, bisdemethoxycurcumin, colour, antioxidant capacity
Turmeric oleoresin exposed to ordinary fluorescent light or to white LED light lost colour and fluorescence significantly, and the white LED caused the greater instability. Each of the three curcuminoids decreased, with curcumin degrading the fastest under both lamps. The authors conclude that the instability of turmeric pigment under common lighting should be taken into account when turmeric-containing products are processed, stored and distributed.
Conditions: Fluorescent light and white LED, both at 10 W/m², against dark storage
What this does not show: Read in the abstract only, which gives no rates or exposure times. The material was an oleoresin, in which the pigment is far more exposed to light than inside particles of ground rhizome.
Measured on the spice
Storage · Retains 1,8-Cineole, borneol, myrcene
Sage leaves dried at 50 °C and then stored for twelve months at room temperature in the dark showed little change in the concentrations of the key odorants that were followed. The authors conclude that the drying, and not the storage, was the more important factor for the changes in sage’s aroma compounds.
Conditions: Room temperature · 12 months · Leaves dried at 50 °C, stored in the dark
What this does not show: Read in the abstract only. Whole leaves from one plant, in the dark; the abstract does not describe the container, and says “selected” key odorants without listing them.
Measured on the spice
Storage · Converts Hydroxy-α-sanshool, hydroxy-β-sanshool, hydroxy-ε-sanshool, pungency
Hydroxy-α-sanshool isolated from Zanthoxylum oleoresin decreased rapidly under UVB light, following second-order kinetics. The contents of hydroxy-α-, hydroxy-β- and hydroxy-ε-sanshool all changed on exposure, and a new compound formed that shares their mass and a similar structure; the authors show that the sanshools undergo isomerisation under UVB.
Conditions: in laboratory solvent · Three sanshools isolated from Zanthoxylum oleoresin and exposed to UVB light in different solvents
What this does not show: Read in the abstract only. Pure compounds in solvents under a UVB lamp, not husks of Sichuan pepper in a jar; it identifies light as a route of loss and gives no rate that applies to the spice.
Measured on the pure compound
Storage
The handbook states that thoroughly dried coriander fruits, stored under dry conditions, will maintain their essential oil for several years without loss, and that once the fruits have been crushed the essential oil quickly disappears.
Conditions: Thoroughly dried fruits stored under dry conditions
What this does not show: A one-line statement in a handbook, with no figures, temperatures or packaging. “Several years without loss” is the handbook’s phrase and is not supported by a study read for this profile.
Documented practice
How to read a finding
A finding belongs to its sample, its method and its conditions.
Each card is one result from one study of one batch. A drying curve fitted in a laboratory dryer describes that dryer; a loss measured over six months at 40 °C describes that package at that temperature. None is a specification, a shelf life or an instruction for processing a crop. A card marked as documented practice records what producers do and measures nothing. Where only the summary of a paper could be read, the card says so. Where studies disagree, both are given and each says so.
Where no finding appears for a spice or a step, none has been read. It does not mean that nothing happens.