Good under pressure


Dr Jon Palmer with a Styrofoam cup that has been subjected to high-pressure pasteurisation

A new device at Massey’s Food Pilot Plant allows food products to be pasteurised at low temperature.

The high-pressure processing machine removes bacteria and pathogens from food products without compromising their nutritional value, flavour, colour or texture.

Institute of Food, Nutrition and Human Health lecturer Dr Jon Palmer says the process exposes food products to high pressure at a low temperature.

“Pressure in the range of 100-700 megapascals (1-7000 times atmospheric pressure) for a period of time, usually two-15 minutes,” he says.

“Many bacteria and yeast are killed by this high pressure, eliminating potential pathogens and extending the shelf life of the product, all at relatively low temperatures.”

By avoiding heat processing, heat sensitive nutrients such as vitamins are retained, as are inherent colours and flavours, giving processed products a natural appearance and fresh taste.

“This process will work best for high-value food products that need to retain those characteristics of nutrition and taste.”

Massey’s new machine has a capacity of two litres, which makes it perfect for product testing, Dr Palmer says.

Packaged food can also be processed in this way, although any air in either the food or the packaging is removed (see image).

The pilot plant, opened in 2008, serves as a facility for teaching students traditional and new processing techniques. Food manufacturers also use the pilot plant for cost effective trials on new product formulations.