Picrocrocin
Also written picrocrocine
Quick answer
The bitter compound of saffron, and the precursor of its aroma: during drying picrocrocin breaks down to release safranal, so the bitterness and the smell of saffron are two stages of one molecule.
What it does
Picrocrocin is a glucoside — a sugar bound to an aroma molecule — and in that bound form it has no smell and a distinct bitterness. It is the reason good saffron tastes faintly bitter and honeyed rather than merely perfumed, and ISO 3632 measures it separately, by absorbance at about 257 nm, as the standard’s index of taste. Its second role matters more: drying splits the sugar off, and what is released is safranal, the compound that makes saffron smell of saffron. A stigma that has been dried well has converted part of its picrocrocin; one that has not smells of very little.
How it behaves when cooked
Four properties of the molecule, and what they mean at the stove.
- Volatility
- low
- Fat solubility
- low
- Water solubility
- high
- Heat stability
- moderate
Water-soluble and not volatile, so picrocrocin comes out into the warm water or stock that saffron is steeped in, along with the water-soluble crocin that gives the colour. That shared solubility is why steeping is the right technique for saffron and frying is the wrong one: the colour and the taste both need water, and the aroma they give rise to is volatile enough that a long boil drives it off. Steep the threads in warm rather than boiling liquid, add the liquid and threads together, and add them late enough in a long-cooked dish that the aroma survives.
Spices that carry it
Recorded on the compound rather than on each spice, so the two cannot disagree.
- SaffronMajor component
Measured as one of the three quality indices in ISO 3632, alongside crocin for colour and safranal for aroma.
What cooking and processing were measured to do to it
Findings from studies in which this compound was followed through heat, fat, water, drying or storage. Each belongs to its study and its conditions.
Steeping and soaking in water · Extracts Picrocrocin
Picrocrocin, the bitter compound of saffron, passed into water easily and was the most stable of the compounds followed: its extraction showed no significant difference across temperatures from 10 to 60 °C. The highest value, 47.6 µg per mg of saffron, was reached at 100 °C in 10 min. Into pure oil it moved only slightly, reaching at most 5.13 µg/mg after 30 min at 100 °C.
Conditions: in water · 10 to 100 °C · 10 to 30 min · Ground saffron in water, olive oil or mixtures of the two
What this does not show: One saffron, ground and stirred. The bitterness of the infusions was not tasted, so the figures describe the compound and not the perceived bitterness.
Measured on the spice
Simmering and boiling · Retains Picrocrocin, Safranal
Picrocrocin proved highly stable in water. Its half-life ranged from more than 3400 h in saffron extract at 5 °C to 9 h for the purified compound in water at 100 °C. In the purified compound at 100 °C, safranal was confirmed to form during the first 5 h, with a yield of up to 7.4 per cent.
Conditions: in water · 5 to 70 °C for saffron extracts; 100 °C for purified picrocrocin · Aqueous extracts and purified compound; second-order kinetics
Over the length of time a dish is cooked, very little of saffron’s bitter compound breaks down, and only a small part of what does becomes aroma. Cooking is not a significant way of making safranal.
What this does not show: Read in the abstract only. Extracts and pure compound in the laboratory, in the dark; the abstract notes that the rate in whole extracts behaved irregularly with temperature, peaking at 35 °C.
Measured on the pure compound
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
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 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
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
Not to be confused with
Compounds a reader is likely to take for this one, and why they differ.
Safranal
Its breakdown product. Picrocrocin is the bitterness and the reservoir; safranal is the aroma. Drying converts one into the other, so the balance between them records how the saffron was processed.
Crocin
The colour compound, and a separate molecule — although both are formed from the same carotenoid precursor in the stigma and both dissolve in water.
Questions this page answers
- what is picrocrocin
- why is saffron bitter
- picrocrocin in saffron