The lactoperoxidase system is an antimicrobial complex naturally present in raw milk, comprising the enzyme lactoperoxidase, thiocyanate ions and hydrogen peroxide — which together generate hypothiocyanite, toxic to many bacteria. It can be activated by adding small, regulated amounts of thiocyanate and H₂O₂ to extend the keeping time of raw milk where refrigeration is unavailable — a Codex-approved method (CAC/GL 13) vital for smallholder dairies in warm climates — and shows promise for preserving other foods. It offers a natural, low-cost hurdle against spoilage and pathogenic bacteria, though it does not replace pasteurisation and is inactivated by heat.