Sodium benzoate was the first chemical preservative permitted in foods by the FDA, and it continues to be widely used in large number of foods. Benzoic acid and its related compounds possess antimicrobial activity and their antibacterial action increases in the presence of CO2 and acid. For example- Bacillus subtilis cannot survive in benzoic acid solution in the presence of CO2.
As used in acidic foods, these act essentially as a mould and yeast inhibitor. In fact, benzoic acid is more effective against yeasts than against moulds. It does not stop lactic acid and acetic acid fermentation. Benzoates have greatest activity at low pH especially in food products with pH below 4.5. Optimum functionality occurs between 2.5 and 4.0 pH. Benzoic acid is mostly used in coloured products of tomato,phalsa, jamun, pomegranate, strawberry, coloured grapes etc. as in the long run, it may darken the product.
Sodium benzoate, sodium salt of benzoic acid, is very effective as it is nearly 180 times more soluble in water than benzoic acid. It produces benzoic acid when dissolved in water. It should be used at low levels to avoid possible off-flavours in some products. The maximum level allowable by PFA act is 0.075 per cent. It is used in fruit products, jams, relishes, beverages etc. and is effective against yeasts, some bacteria (food borne pathogens but not spoilage bacteria) and some moulds.
Sorbic acid and related compounds
Sorbic acid and related compounds have antimicrobial properties. They are available as sorbic acid, potassium sorbate, sodium sorbate or calcium sorbate. Salts of sorbic acid are used in many cases as they are highly soluble in water and produce sorbic acid when dissolved in water. The potassium salt of sorbic acid i.e. potassium sorbate is much more soluble in water than the acid. It does not impart any noticeable flavour at normal usage concentrations. Maximum level allowable by PFA act is 0.3 per cent. It is effective up to pH 6.5 but effectiveness increases as the pH decreases. It has about 74 per cent of the antimicrobial activity of the sorbic acid, thus it is required in higher concentrations than pure sorbic acid. It is effective against yeasts, moulds, and select bacteria, and is widely used at 0.025 to 0.10 per cent levels in cheese, beverages, fermented and acidified vegetables, smoked and salted fish. In wine processing, sorbates are used to prevent refermentation.
Propionic Acid and Related Compounds