Inactivation of Escherichia coli O157:H7 and Staphylococcus aureus in red pepper powder using a combination of radio frequency thermal and indirect dielectric barrier discharge plasma non-thermal treatments

This investigation evaluated the inactivation of foodbome pathogens and quality of red pepper (Capsicum annuum L.) powders treated via intermittent intervention with a combination of radio frequency thermal treatment (RF-TT) and dielectric barrier discharge plasma treatment (DBD-PT). Microbiological analysis of powders inoculated with Escherichia coli O157:H7 and Staphylococcus aureus following RF-TT and DBD-PT combination indicated reductions in the microbial counts proportional with increasing treatment cycles. The combination of 1500 W RF heating and 1000 W DBD-PT treatment reduced microbial counts to below the detection limit (1 log CFU/g) after 2 repetitions of the treatment cycle. RF-TT and DBD-PT combination (5 cycles) did not affect powder extractable colour or free radical scavenging activity. The combined treatment caused negligible changes in CIE L*, a*, b*, and Delta E* and extractable colour values. The moisture content and water activity showed significant (p < 0.05) differences compared to the control, likely owing to the drying of samples during intermittent RF-TT and DBD-PT. Thus, the hurdle technology combining RF heating and non-thermal plasma treatment could be useful in improving the microbiological quality of red pepper powder.