Mild Heat and Microwave Inactivation of Escherichia coli and Saccharomyces cerevisiae in Pomegranate Juice

Pomegranate juice is a rich source of functional ingredients which thermal processing significantly affects its functional compounds. In this study, the effect of mild heat and microwave processing on the inactivation of inoculated microorganisms in pomegranate juice was studied. The juices were processed with mild heat treatment (۵۲, ۵۴, ۵۶, ۵۸ and ۶۰°C for ۰ to ۱۲۰ s) and also with a domestic microwave at ۶۰۰ W (for ۰, ۴۵, ۶۰, ۶۷.۵, ۷۵, ۸۰, and ۹۰ s) and ۹۰۰ W (for ۰, ۳۰, ۴۰, ۴۵, ۵۰, and ۶۰ s). Mild heat (at ۶۰°C for ۱۲۰ s) and microwave (۶۰۰ and ۹۰۰ W for ۹۰ and ۶۰ s, respectively) treatments led to a reduction of approximately ۶.۶۵ log cycles in E. coli and ۵.۰۶ log cycles in S. cerevisiae. The mild temperature of ۵۸°C for ۱۲۰ s reduced S. cerevisiae to below the detection limit, while the population of E. coli was inactivated at ۶۰°C for ۱۲۰ s. Also, the S. cerevisiae load at ۶۰۰ W/۸۰ s and ۹۰۰ W/۵۰ s was less than the detection limit. But, the E. coli load at ۶۰۰ W/۹۰ s and ۹۰۰ W/۶۰ s were less than detection limit. The type of pomegranate juice did not have a significant effect on microbial inactivation in both mild heat and microwave processes. Similar to mild heat treatment, S. cerevisiae was more sensitive than E. coli at both microwave powers.

کلیدواژه ها:

Electromagnetic wave ، fruit juice ، Microbial inoculation ، Sub-pasteurization