Citric acid
Also written citric, citric and malic acids
Quick answer
The sharp, clean sourness of citrus and of most dried souring spices — the acid that tastes immediately of sourness and then gets out of the way.
What it does
Citric acid is sour in the most direct sense: a fast, bright, clean sourness that peaks quickly and fades without leaving anything behind. It is the reference point most people carry for what sour means, because it is the dominant acid in lemons and limes. In a spice it reads as lift rather than as body — a squeeze of brightness that does not change the character of the dish it is added to. That is precisely why amchur and dried lime can be used to sour a dish that must not taste of fruit.
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
- high
Highly water-soluble, not volatile and stable to heat, which together mean that a citric souring agent behaves nothing like an aromatic spice. It does not cook off, it does not need blooming in fat, and it disperses instantly into any watery phase — so it can be added at the end and adjusted, which is the opposite of how the aromatics in the same dish must be handled. Two practical consequences follow. Acid added early to a long braise stays at full strength while the liquid reduces around it, so a dish soured at the start is sharper at the end than it was. And because acid slows the softening of pulses and vegetables, a souring spice belongs after the beans are tender rather than before — which is the reason amchur and dried lime are late additions in the traditions that use them.
Spices that carry it
Recorded on the compound rather than on each spice, so the two cannot disagree.
- AmchoorPrincipal component
The reason amchur sours without tasting of mango: the acid is prominent and the fruit character is faint.
- Dried limePrincipal component
- AnardanaMajor component
- BarberryMajor component
- Pomegranate molassesMajor component
The leading organic acid in five bottled pomegranate sours bought in Malatya, as in fresh juice pressed beside them; the sourness of the concentrate is reckoned as citric acid in the Turkish registrations and standard.
- RoselleContributing component
The accounts disagree. A handbook puts citric acid at about 4 per cent of the calyx and a review names it among the main acids, without amounts. The one study read that measured it, by liquid chromatography in three Mexican varieties, found 4 to 29 mg per 100 g of dry calyx, the fourth of the five acids it measured. That study had no standard for hibiscus acid, so its ranking is of five acids only, and one study of three varieties does not settle the matter. Total acidity expressed as citric acid by titration, as several reports give it, is not a measurement of citric acid.
- SumacContributing component
- KokumPresent in small amounts
Not what makes kokum sour. The acid of the rind is hydroxycitric acid; when the rind’s acids were measured, citric acid was found beside it only in minor quantities.
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.
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
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
Not to be confused with
Compounds a reader is likely to take for this one, and why they differ.
Malic acid
The other acid in most of these spices, and the difference a cook can taste. Malic is slower, rounder and lingers; citric is sharp and brief. A souring agent where malic dominates reads as fruity, one where citric dominates reads as simply sour.
Hydroxycitric acid
The acid of kokum and kudampuli: citric acid with one more hydroxyl group, and a different compound. Where a Garcinia rind is described as sour, this is the acid measured in it, with citric acid found only in minor quantities in kokum.
Tartaric acid
The harsher third acid, prominent in tamarind and in grapes. It is the one that reads as astringent as well as sour, which is why tamarind cannot be replaced by lemon juice without the dish losing a dimension.
Ascorbic acid — vitamin C
Present in citrus alongside citric acid and contributing almost nothing to the taste. The two are routinely conflated, and it is citric acid that makes a lemon sour.
Questions this page answers
- what is citric acid
- what does citric acid do
- which spices contain citric acid