Antioxidants

Fats and oils in food are prone to oxidation, and oxidised fat turns rancid -- the unpleasant taste and smell everyone recognises in stale cooking oil or old snack food. Antioxidants are the additives that slow this down: BHT (butylhydroxytoluene) and BHA (butylated hydroxy anisole) are the two named examples. Mechanistically, they work by readily reacting themselves with the free radicals generated as oils begin to oxidise -- by sacrificially consuming those radicals, they interrupt the chain reaction that would otherwise propagate the oxidation right through the food. Sulphur dioxide and sulphites serve a related but broader purpose as food additives: they act simultaneously as anti-m …