Tartaric acid substitutes

The closest widely available acid powder, sold in the same aisle and doing the same three jobs.

Best for

Turkish delight, sherbet powder, hard candy, lemonade and cordials, sour dusting

This is the practical answer. Tartaric acid is a little sourer per spoonful than citric, so you need slightly more citric to land in the same place. The difference you will taste is the shape of the sourness rather than the amount: tartaric is a fast, clean, almost wine-like sour that arrives and leaves quickly, while citric reads distinctly lemony and stays brighter on the tongue. In Turkish delight it works identically as the acid that inverts some of the sugar and keeps the set glossy instead of grainy. In sherbet powder the fizz is exactly the same, because the bicarbonate only needs an acid to react with and does not care which one.

The potassium salt of tartaric acid, which is related but is a much weaker acid.

Best for

stabilising egg whites, stopping sugar syrups crystallising, biscuits and scones, royal icing

Worth being clear about, because this is the single most common mix-up: cream of tartar is potassium bitartrate, a salt made from tartaric acid, not the acid itself. It is roughly a third to a half as acidic spoon for spoon, and it barely tastes sour, more chalky and faintly mineral. That means it is a good swap where you only need an acid to do a job quietly, such as keeping a sugar syrup smooth or helping meringue hold, and a poor one where the sourness is the point. Sherbet powder made with cream of tartar tastes flat and slightly powdery rather than sharp.

The acid of green apples, sold as a powder in the same candy-making suppliers.

Best for

sour candy, sour powders, fruit sweets, seasoning blends

Malic acid is slightly less sour than tartaric spoon for spoon, so use a touch more. The character is noticeably different in a way you will taste immediately in a sweet: tartaric hits hard and disappears, while malic builds more slowly and then hangs around for ages, with a green-apple edge behind it. That lingering quality is exactly why extreme sour candy uses malic. If you are making Turkish delight it does the anti-crystallisation job just as well and nobody will notice.

Fresh acid you almost certainly already have, at the cost of adding liquid.

Best for

sugar syrups, Turkish delight, drinks and sharbats, jams and fruit curds

Three tablespoons is about 45 ml of extra liquid, which is fine in a sugar syrup you are going to boil anyway and hopeless in a dry mix. The flavour goes obviously lemon, which is welcome in a drink and slightly odd in a rose or pistachio Turkish delight. If you are boiling a syrup you can add the lemon juice early and simply cook it a minute or two longer to drive off the water.

A strong, neutral-tasting liquid acid for savoury and boiled applications.

Best for

savoury sauces, boiled sugar syrups, brines for immediate use

Vinegar lowers pH efficiently, but it smells like vinegar and that smell survives in anything you do not cook for a while. In a boiled candy syrup the sharp aroma mostly cooks off and you are left with a clean sourness that is acceptable. In a sherbet or a cold drink it is unpleasant. Treat this as the option you reach for when you need acidity and not flavour.

The least-bad option when you only need something acidic and have nothing else.

Best for

stopping cut fruit browning, dough conditioning, mild pH adjustment

Be honest with yourself about what you need. Ascorbic acid lowers pH but tastes only faintly sour and slightly bitter, so a sherbet or a sour sweet made with it tastes strangely blank. It is genuinely useful for keeping apples and pears from browning and as a dough improver, and it is a poor stand-in anywhere the sourness is meant to be tasted.