Inactivation of Escherichia coli O157:H7 and Salmonella Typhimurium on Black Peppercorns Using Simultaneous Radiofrequency and Nonthermal Plasma Treatment: Efficacy and Impact on Quality

Abstract

This study evaluated the inactivation of Escherichia coli O157:H7 and Salmonella Typhimurium and impact on quality of black peppercorns using radiofrequency (RF), nonthermal plasma (NTP), and their simultaneous combined treatment (RF-NTP). RF-NTP achieved full elimination of both pathogens on black peppercorns within 13 min, whereas RF alone required 17 min to achieve the same level of inactivation. The increased inactivation efficacy of RF-NTP resulted from synergistic effect of RF heating and the reactive oxygen and nitrogen species generated from NTP. The inactivation kinetics of pathogens on black peppercorns with RF, NTP, and RF-NTP fitted the Weibull model (R2 > 0.96, RMSE < 0.35). RF-NTP reduced maximum temperature of black peppercorns to 68.9 °C, compared to 84.2 °C for RF. Among the ten predominant flavor volatiles of black peppercorns, RF-NTP retained six compounds while RF preserved only three (p < 0.05), salvaging β-caryophyllene, β-selinene, and δ-cadinene. Additionally, RF-NTP lowered water activity of black peppercorns from 0.643 to 0.402 without impacting color or chemical bonds of the sample surface. In conclusion, RF-NTP demonstrated greater efficacy for pathogen control on black peppercorns compared to RF alone, while also better maintaining flavor compounds, indicating its potential as an effective intervention for thermal sensitive spices.