Malonaldehyde — systematically malondialdehyde (MDA) — is one of the principal aldehydes produced as a result of lipid oxidation, formed when polyunsaturated fatty-acid hydroperoxides decompose. It is traditionally measured in the thiobarbituric acid (TBA) test, where it condenses with thiobarbituric acid under heat and acid to form a pink chromophore; the resulting TBA value (or TBARS value) is a standard index of lipid rancidity and oxidative deterioration in edible oils, meats, fish and fried snacks. Because it is itself reactive and potentially mutagenic, minimising its formation matters for safety as well as sensory quality — processors control it with antioxidants, oxygen exclusion, proper frying-oil management and cold storage.