Effect of radio frequency heating stress on sublethal injury of Salmonella Typhimurium in red pepper powder
2020
Abstract Radio frequency (RF) heating has been explored as a new pasteurization technology for low-moisture foods (LMFs). This study investigated the impact of RF heating on sublethal injury of Salmonella Typhimurium in red pepper powder with different initial water activity (aw) (0.44, 0.53, 0.63 and 0.70). Red pepper powder inoculated with Salmonella Typhimurium (7 log CFU/g) was treated by RF heating (70 °C, 3 min) with heating rate of 10 °C/min. Results showed that there were sublethal injured cells (SICs) in the powder with initial aw≥0.53 after RF treatment, but no SICs in the samples with initial aw of 0.44. To confirm this result, influence of repair conditions (temperature, time and selective medium), RF heating rate (1.9–17.6 °C/min) and pasteurization temperature (60–100 °C) were studied on the powder with aw of 0.44. The tested repair conditions showed no significant (p > 0.05) influence on injury ratio of Salmonella Typhimurium, and changing RF pasteurization temperature or heating rate did not cause generation of SICs. These results confirmed that there were no SICs of Salmonella Typhimurium in red pepper powder with initial aw of 0.44. The information generated from this study is valuable for developing RF pasteurization treatment for LMFs.
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