Abstract
High Electric Field AC (HEF-AC) is an instantaneous microbial inactivating treatment based on two electrical effects: own-generated Joule heat by electric current flowed into food, and cell membrane injuries caused by applied electric field. In this study, we applied three types of heat-resistant microorganisms: mesophilic-, thermophilic-, and acidophilic organisms, to a device of continuous pressurized HEF-AC. We examined the effect of treatment condition for inactivation against B. subtilis spore. The inactivation effect was improved in proportion to the temperature above 113°C as onset inactivation temperature of B. subtilis. We take D-value as the rise in temperature with decrease the number of bacteria to one tenth. Triple intensity of electric field effected a reduction of D-value and a logarithmic order inactivation at 115°C. On the other hand, Triple electric current had little effect on inactivation. In the comparison with D-value between HEF-AC and UHT, the D-value through the use of HEF-AC was smaller than that of UHT: the inactivation effect through the use of HEF-AC was higher than that of UHT. Double intensity of electric field effected a reduction of D-values and an increase of inactivation of other 4 species of heat resistant microorganisms. It was found that the higher D-value of microorganism spores could be effectively improved the inactivation effect by applying higher electric field. It was found that each microorganism' s onset inactivation temperature through the use of HEF-AC was increased in proportion to logarithm of F-value as an index of heat-resisting properties of the microorganism.
