Because food is so important to survival, food preservation is one of the oldest technologies.

Because food is so important to survival, food preservation is one of the oldest technologies. Different ways and means have been found and improved for the purpose, including the traditional methods of boiling, freezing, refrigeration, pasteurising, dehydrating and pickling.

Chemical preservatives have been used for many years. Preservatives are ingredients that either retard the growth of microorganisms or kill them. The three main groups of food spoilage microorganisms are bacteria, yeasts and moulds.

The five main preservatives we usually encounter in the food industry are:

• Calcium propionate (calcium salts of propionic acid)
• Sorbic acid and potassium sorbate (potassium salt of sorbic acid)
• Sodium benzoate (sodium salt of benzoic acid)
• Sodium lactate
• Sodium metabisulphide (the most commonly used form of sulphur dioxide)

The functional part of these ingredients is usually found in the acid form. However, propionic acid, sorbic acid and benzoic acid are all relatively insoluble in water. While the salts are more soluble, all dissociate into their active form at various pH’s and may not be active under certain conditions.

HWG offers the following preservatives:

Calcium Propionate

Effective against mould and has very little antibacterial action and very slight activity against yeast. Since there is no significant effect against yeast, calcium propionate can be used in yeast raised products, such as bread.

Sorbic acid and potassium sorbate (potassium salt of sorbic acid) are effective against yeast and mould, but with little activity against bacteria. Sorbic acid has low solubility in water, which increases with increasing temperature, while potassium sorbate is readily soluble in water.

Potassium sorbate has the best activity (greater dissociation into sorbic acid) up to pH 5.5 but will usually have some effect up to pH 6.5. Potassium sorbate is widely used in cheese, fruit products and chemically leavened baked goods.

Potassium Sorbate: effect of pH

Sodium benzoate is effective against yeast and has some effect against bacteria and mould. The most effective pH range for sodium benzoate is pH 2.5 to 4.0, although it can sometimes be used up to pH 4.5. It is commonly used in fruit products and carbonated beverages.

Sodium lactate is gaining greater use in meat products to extend shelf life. Typical dose rates can run up to 2%, and it is thought to be effective at reducing bacterial spoilage by reducing the water activity of the product

Disclaimer The maximum dose rates of all products are prescribed by law, and you must check these out: Food Standards Australia New Zealand (FSANZ)