Malic Acid
What it does
Sour flavour, acidity regulator.
How it's made
Synthesised or from fruit.
Malic acid is the acid that makes apples and many other fruits taste tart, and it is widely used to give a clean, long-lasting sourness to sweets, drinks and desserts. It occurs naturally throughout the plant world, but the quantities used in food manufacturing are produced industrially rather than extracted from fruit.
Most food-grade malic acid is made synthetically by taking maleic or fumaric acid — derived from petrochemical feedstocks — and adding water across a double bond (hydration) at high temperature and pressure, often with a catalyst. This produces a mixture of the two mirror-image forms of malic acid, unlike fruit, which contains only one form; both are handled normally by the body.
After the reaction the acid is purified by crystallisation and drying to give the white food-grade powder. A smaller amount is produced by fermentation using microbes, but the synthetic hydration route accounts for most of what is used in food because it is efficient and produces a consistent, high-purity product.
Possible reactions
Generally safe; naturally in apples.