Optimization of Cold Sterilization Process and Its Effect on Quality of Dried Jujube by High Voltage Electric Field Cold Plasma

The issue of food safety and quality caused by microorganism contamination of dried fruit food such as dried jujube has attracted more and more attention. At present, high voltage electric field cold plasma (HVEF-CP) technology is one of the research hot spots worldwide. This paper studied the sterilization efficiency on dried jujube fruit of HVEF-CP technology by response surface method, with the working frequency, the voltage and the working time as the test factors, in order to optimize the sterilization parameters. Samples were taken every 15 days to study the changes of the total number of bacterial colonies, the total number of mold and yeast and the number of coliform bacteria on the dried fruit surface in the accelerated storage period experiment. The results showed that the sterilization efficiency was significant increased and then tended to be flat with the rising of working frequency, voltage and time under certain conditions (P<0.05). The optimal conditions after optimization were given: Voltage intensity of 65 kV, treatment time of 150 s, and working frequency of 86 Hz. The sterilization efficiency of total bacterial count could reach to 99.6% under the optimum technological conditions. Compared with ultraviolet sterilization, the HVEF-CP technology took less time and had better sterilization effect, and had no significant effect on the quality. At the same time, it could effectively inhibit the growth of the total number of bacterial colonies, the total number of mold and yeast, and the number of coliform bacteria in the storage period, so as to prolong the storage period of dried jujube fruit for 50 days.