Effects of processing parameters on the inactivation of Bacillus cereus spores on red pepper (Capsicum annum L.) flakes by microwave-combined cold plasma treatment

- Microwave-combined cold plasma (MCP) effectively inactivates B. cereus spores.
- MCP at high microwave power effectively inactivates spores on red pepper powder.
- Spore inactivation by MCP is efficient with vacuum-dried powder with smooth surface.
- The inactivation effect of MCP is higher when red pepper is prepared in larger pieces.
- Increased water activity in the powder enhances spore inactivation by MCP treatment.

The efficacy of microwave-combined cold plasma treatment (MCPT) for inactivating Bacillus cereus spores contaminating red pepper (Capsicum annum L.) flakes was investigated. The effects of red pepper drying method, particle size, and water activity (aw) were also evaluated at two levels of microwave power (1700 and 2500 W/cm2). The inactivation effect of MCPT was higher at higher microwave power. Spore reduction was more effective with vacuum-dried red pepper than far-infrared-dried flakes. A significantly higher level of spore reduction was observed with the red pepper sample with a smaller surface to volume ratio when one surface (exterior surface) was inoculated (p < 0.05). Spore reduction by MCPT at high microwave power increased from 1.7 to 2.6 log spores/cm2 when the aw of flake increased from 0.4 to 0.9 (p < 0.05). MCPT did not change the color of red pepper flakes. MCPT demonstrated potential as a microbial decontaminating technology for red pepper flakes.