Preservation by irradiation is also called ionisation, whereby food is exposed to gamma rays, X-rays or electron beams. Ionising radiation penetrates the foodstuff, including the packaging, and releases energy. This energy destroys bacteria and causes reactive particles to form, which react with the food components within a fraction of a second. This process inhibits germination, slows down decay, kills pathogenic microorganisms and destroys insects and their larvae. Following the use of irradiation, other innovative preserving techniques emerged during the 20th century, such as pascalisation or high pressure processing (HPP), microfiltration and biopreservation.
Pascalisation is where food products are subjected to very high pressure of up to 6000 bar, bearing in mind that 10 km below sea level the pressure is 1000 bar. This high-pressure processing is also called cold pasteurisation. It prolongs the shelf-life of food by causing a reduction in bacterial flora. It also slightly changes the colour and taste of food, but does not alter the vitamin content at all.
Microfiltration is a technique involving the physical separation of components. It uses filter membranes with pore sizes ranging from 0.1 to 10 micrometres in diameter and is used to destroy bacteria in liquids.
The biopreservation of food involves adding microorganisms to food, generally packaged in a protective atmosphere. The microorganisms have been selected for their ability to inhibit the growth of other undesirable microorganisms. This technique seems to be a good alternative to methods which use chemical food additives.