Citric acid

Acide citrique

What it is

Carl Wilhelm Scheele crystallised it out of lemon juice in 1784, and for more than a century the world's supply came from Italian lemons held by a growers' cartel. Then a Pfizer chemist, James Currie, found that the mould Aspergillus niger fed on sugar would excrete it by the vat, and the lemon monopoly was finished within a few years.

In the kitchen

One gram in a litre gives roughly the acidity of 20 ml of lemon juice, without the water or the peel oil — you weigh it in for precision, not economy. Dissolve it in a spoon of water and add it off the heat: sprinkled dry into a hot purée it makes local hot spots of acid that curdle dairy and split a sauce.

Goes with

Lemon Tomato Apricot Strawberry White sugar Raspberry Apple

Also used with

Yellow pectin

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