Date of this Version
Xinyao Wei (2017). Radiofrequency processing for inactivation of Salmonella spp. and Enterococcus faecium NRRL B-2354 in whole black peppercorn and ground black pepper (M.S. Thesis).
Black pepper has been implicated in several foodborne illness outbreaks and food product recalls due to Salmonella contamination. Conventional decontamination methods for black pepper are challenged by harmful residues or quality deterioration. Radiofrequency (RF) heating reduces the come-up time which allows to design a high-temperature short-time processing to inactivate Salmonella with minimal deterioration in product quality. The objectives of this study were to investigate RF heating for inactivation of Salmonella in whole black peppercorn and ground black pepper samples, evaluate Enterococcus faecium NRRL B-2354 as a surrogate for Salmonella, and assess quality deterioration during RF heating of whole black peppercorn and ground black pepper samples. Both samples were inoculated with a 5-strain cocktail of Salmonella or E. faecium, equilibrated to the target water activity, and RF heated for 150 s for whole black peppercorn and 130 s for ground black pepper. Microbial stability and homogeneity tests were conducted for both Salmonella and E. faecium during moisture equilibration before RF heating to evaluate the inoculation method. Piperine, total phenolic and, volatile oil, and the antioxidant activity were assessed for the quality of both whole black peppercorn and ground black pepper samples. RF heating was demonstrated to provide 5.31 and 5.98 log CFU/g reduction of Salmonella for whole black peppercorn and ground black pepper, respectively. Whole black peppercorn and ground black pepper samples were dried to their optimal storage moisture after RF heating. The higher thermal resistance of E. faecium was observed during RF heating of both black pepper samples. The quality analysis showed that the quality of both black pepper samples did not experience a considerable change after RF heating. In this study, an applicable RF pasteurization process was developed for whole black peppercorn and ground black pepper, which provided effective inactivation of Salmonella while minimizing the quality deterioration. E. faecium was found to be a suitable surrogate for Salmonella during the RF heating of both whole black peppercorn and ground black pepper samples.
Advisors: Jeyamkondan Subbiah & Jayne Stratton