Anthocyanins
Also written anthocyanin
Quick answer
The red-to-purple-to-blue pigment family, and the only colour in this catalogue that changes with acidity — which is why a shiso pickle turns scarlet and a red cabbage turns blue.
What it does
Anthocyanins are a family rather than a single compound, and the profile is named in the plural deliberately: cyanidin, delphinidin and their relatives differ, and the spices here do not distinguish between them. What they share is the property that makes them worth a page — their colour depends on pH. In acid they are red, at neutral they are purple, in alkaline conditions they shift towards blue and green. They also carry a mild astringency, which is part of why the fruits that hold them taste as they do.
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
- low
Two properties govern everything: they are water-soluble and their colour answers to acid. Being water-soluble, they leach — a sumac or a barberry simmered in a stock colours the stock rather than the dish, which is why both are usually scattered on at the end. Being pH-sensitive, they are the one pigment a cook can deliberately steer: red shiso leaves packed with salt and umeboshi turn a vivid scarlet because the plum brine is acidic, and the same leaf in a neutral dish stays a dull purple. That is a technique rather than an accident, and it is the mechanism behind the colour of Japanese pickles. They also degrade with sustained heat, so a long-cooked anthocyanin dish goes brown — the reason barberries are added to a rice dish near the end rather than cooked through it. How fast they go depends on the acid as well: an extract of roselle calyx heated at pH 2 kept 88 per cent of its anthocyanin after two hours at 70 °C and 60 per cent after two hours at 90 °C, while at pH 7 less than a third was left after half an hour. The same extract was dark red at pH 1, nearly colourless at pH 5 and blue at pH 7.
Spices that carry it
Recorded on the compound rather than on each spice, so the two cannot disagree.
- BarberryPrincipal component
The jewel red of zereshk polo, which is lost if the berries are cooked through the rice rather than added late.
- RosellePrincipal component
The red of the dried calyx and of the drinks made from it, chiefly delphinidin-3-sambubioside and cyanidin-3-sambubioside. One lot of dehydrated calyces held about 362 mg per 100 g, measured as cyanidin glucoside.
- ShisoPrincipal component
Red shiso is the clearest culinary demonstration of the pH effect anywhere: the leaf is dull purple until it meets the acid of umeboshi brine, and then it is scarlet.
- SumacPrincipal component
The deep red, and the reason sumac is scattered over a finished dish rather than cooked into it.
- KokumMajor component
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.
Capsanthin
The other red in this catalogue, and the opposite in every practical respect: capsanthin is a fat-soluble carotenoid indifferent to pH, anthocyanins are water-soluble and answer to acid. Substituting one red spice for another without knowing which pigment is involved is how a dish ends up the wrong colour.
Betalains
The pigment of beetroot, frequently assumed to be an anthocyanin and chemically unrelated. It is not pH-responsive in the same way, which is why beetroot does not do the shiso trick.
Questions this page answers
- what is anthocyanins
- what does anthocyanins do
- which spices contain anthocyanins