Acidulant

Acidulants usually get one line in a recipe, which understates what they do. They set how tart something tastes, help keep it safe, affect color and setting, and change how the flavor comes across.

The common ones, and how they differ

• Citric — fast, sharp, clean, gone quickly. The default for fruit flavors.
• Malic — slower to arrive, rounder, lasts longer. Standard in green apple and sour candy, where duration is the point.
• Tartaric — the sharpest of the group. Associated with grape.
• Phosphoric — flat acidity with no fruit character. The cola one.
• Lactic — mild, slightly dairy. Used where you want softness.
• Fumaric — very strong for its weight, poorly soluble. Used in dry mixes and for coating sour candy.

Why it matters to the flavor

Lowering the pH speeds up the breakdown of some flavor compounds — citrus most of all — so a more acidic product loses its flavor faster.

It also changes what you taste right now. The same fruit flavor at pH 3.0 and pH 3.6 comes across as two different products.

Which is why the acid and the flavor should be developed together. A sour system locked in before the flavor is chosen almost always has to be reworked afterwards.