Investigation of non-thermal sterilization method of packed fresh foods using pulsed barrier discharge

It is important to secure food safety. Every year many people suffer from food poisoning by eating a food sterilized insufficiently. For prevention of the food poisoning, sufficiently sterilizing foods and preventing bacteria attaching to the foods are necessary. A packing food in a bag is useful to prevent bacteria attaching. Moreover, if the packaged food can be sterilized, the food poisoning can be reduced considerably. A heated food can be sterilized by heat. However, a fresh food, e.g. a salad, cannot be sterilized by the heat. Therefore we are studying sterilization methods for a packaged fresh food. In this study, we have investigated the applicable possibility of the sterilization method using cold plasma for the packaged fresh food. A petri dish with a lid was used for simulating a packaging bag. The cold plasma was generated into the petri dish by barrier discharge applying pulsed voltage. E. coli on a culture medium was used for a target of sterilization. As a result, it was found that sufficient sterilization effect is obtained by applying 500 pulses of 40 pps, 90 kV and 120 ns of FWHM. The temperature and pH of the petri dish didn't change at applying 500 pulses. Also degree of decolorization of indigo carmine solution was investigated for evaluation of influence on foods under same condition. The degree of decolorization was only 2.6 %. This method can be applied as the non-thermal sterilization for packaged fresh foods.