The synergistic efficacy of a combined treatment of mild heat (MH) and dielectric barrier discharge (DBD) plasma in Bacillus cereus-contaminated red pepper powder was tested. A cocktail of three strains of B. cereus (NCCP 10623, NCCP 14579, ATCC 11778) was inoculated onto red pepper powder and then treated with MH (60 °C for 5-20 min) and DBD plasma (5-20 min). Treatment with MH and DBD plasma alone for 5-20 min resulted in reductions of 0.23-1.43 and 0.12-0.96 log CFU/g, respectively. Combined treatment with MH and DBD plasma was the most effective at reducing B. cereus counts on red pepper powder, and resulted in log-reductions of ≥ 6.0 log CFU/g. The largest synergistic values (4.24-4.42 log) against B. cereus in red pepper powder were obtained by the combination of 20 min MH and 5-15 min DBD plasma. The values of Hunter color ''L'', ''a'', and ''b'', were not significantly different from those of the untreated sample and that with the combination of MH (60 °C for 5-20 min) and DBD plasma (5-20 min). Also, no significant (p > 0.05) differences in pH values between samples were observed. Therefore, these results suggest that the combination of MH treatment and DBD plasma can be potentially utilized in the food industry to effectively inactivate B. cereus without incurring quality deterioration of red pepper powder.
Keywords: Bacillus cereus; dielectric barrier discharge plasma; food safety; mild heating; quality; red pepper powder.