<P> Approximately 500,000 tons of food items are irradiated per year worldwide in over 40 countries . These are mainly spices and condiments with an increasing segment of fresh fruit irradiated for fruit fly quarantine . </P> <P> Pulsed electric field (PEF) electroporation is a method for processing cells by means of brief pulses of a strong electric field . PEF holds potential as a type of low - temperature alternative pasteurization process for sterilizing food products . In PEF processing, a substance is placed between two electrodes, then the pulsed electric field is applied . The electric field enlarges the pores of the cell membranes, which kills the cells and releases their contents . PEF for food processing is a developing technology still being researched . There have been limited industrial applications of PEF processing for the pasteurization of fruit juices . To date, several PEF treated juices are available on the market in Europe . Furthermore, for several years a juice pasteurization application in the US has used PEF . For cell disintegration purposes especially potato processors show great interest in PEF technology as an efficient alternative for their preheaters . Potato applications are already operational in the US and Canada . There are also commercial PEF potato applications in various countries in Europe, as well as in Australia, India, and China . </P> <P> Modifying atmosphere is a way to preserve food by operating on the atmosphere around it . Salad crops that are notoriously difficult to preserve are now being packaged in sealed bags with an atmosphere modified to reduce the oxygen (O) concentration and increase the carbon dioxide (CO) concentration . There is concern that, although salad vegetables retain their appearance and texture in such conditions, this method of preservation may not retain nutrients, especially vitamins . There are two methods for preserving grains with carbon dioxide . One method is placing a block of dry ice in the bottom and filling the can with the grain . Another method is purging the container from the bottom by gaseous carbon dioxide from a cylinder or bulk supply vessel . </P> <P> Carbon dioxide prevents insects and, depending on concentration, mold and oxidation from damaging the grain . Grain stored in this way can remain edible for approximately five years . </P>

List out some traditional methods of preserving foods