Preservative

A preservative is a food additive that slows the growth of microbes, such as bacteria, moulds and yeasts, so that food lasts longer. Malay: bahan pengawet · Chinese: 防腐剂.

Food spoils when microbes grow on it and break it down. A preservative works by making conditions difficult for those microbes, so they multiply slowly or not at all, and the food stays safe and edible for a longer time. Common preservatives include salt and sugar, which draw water out of microbe cells, and chemical preservatives such as sodium benzoate and sodium nitrite. Traditional methods like salting fish, drying, and adding plenty of sugar to jam all work on the same principle of holding back microbial growth.

Example. Sodium benzoate is added to bottled fruit juice and sauces to stop bacteria and moulds from growing, so the product keeps for months on the shelf instead of spoiling within days. Salted fish and sweetened condensed milk are older examples of the same idea.

Confusion to avoid. Do not confuse a preservative with an antioxidant. A preservative slows the growth of microbes; an antioxidant slows oxidation and stops fats from turning rancid. Both help food last longer, but they fight different causes of spoilage, so name the right one for the right problem in an exam answer.

The preservative is one of the standard food additives in this chapter, and the usual question asks you to name it and state that it slows microbial growth, a pairing that SPM Chemistry rewards whenever food additives are set. Remember that everyday salt and sugar count as preservatives too, so a question about salted fish or jam is really asking about preservation by drawing water out of microbe cells. Being able to give both a traditional example and a chemical one, and to say clearly that the target is microbial growth, is what turns a one-word answer into a full explanation.