Preservatives

The preservative that is chosen for a particular product will depend on the process conditions. Important factors are the acidity of the product and the water activity as water is essential for microbial growth. The type of organism that might be present in the food is also important. The risk in canned meats, for example, is the deadly botulism bacterium, against which nitrites are uniquely effective. Sorbic acid and sorbate salts are used in products like cheeses and sausages, where they control a broad range of yeasts and moulds. Other antimicrobial substances are also useful preservatives, for example nisin, which is naturally present in certain cheeses as a result of the fermentation processes.

Benzoates are effective in more acidic foods such as soft drinks, while propionates are particularly active against yeasts and moulds in baked goods such as bread. Sulphur dioxide, meanwhile, has been used as a food preservative for centuries, and it is still used today because of its antimicrobial action, its ability to prevent food such as fruit going brown, and the fact that it also acts as an antioxidant..

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