How commercial ketchup stays safe for up to two years unopened

An unopened bottle of commercial ketchup can stay safe to eat for a year or two after its printed date, a Deccan Herald report said. That durability is not down to any single ingredient but to acidity, thick tomato solids, sugar, heat treatment during manufacture and sealed packaging acting together to keep bacteria from growing. Vinegar brings the pH down to roughly 3.3 to 4.0, and salt and sugar tie up the water microbes would otherwise use. The report traces the recipe back to the late 1800s, when Heinz chemists raised the proportion of tomato pulp and balanced it with extra sugar and vinegar specifically so the ketchup would not need sodium benzoate, a preservative many Indian brands still use today under permitted limits. Exposed to heat or light, sodium benzoate can react with vitamin C to form small amounts of benzene, and reproducing a preservative-free formula at scale needs tightly controlled acidity, pH and microbiology because tomato paste itself varies from batch to batch.