Exploration of Surrogate Bacteria of Salmonella in Black Pepper (Piper nigrum) Kernels Under Radio Frequency Sterilization Conditions

Abstract:

This study was conducted to explore the feasibility to use Enterococcus faecium NRRL B-2354 (E. faecium) as a surrogate for Salmonella typhimurium ATCC 14028 (S. typhimurium) in black pepper during thermal processing. The thermal resistance parameters of E. faecium and S. typhimurium in black pepper were detected by isothermal experiments. Furthermore, an experimental verification of radio frequency sterilization for black pepper kernels (A_w=0.65) was carried out. The results of the isothermal experiments indicated that the heat resistance of E. faecium was higher than that of S. typhimurium in black pepper kernels. In the radio frequency (RF) sterilization experiment, 2 g of inoculated black pepper kernels with both bacteria strains were vacuum-sealed and placed in the center of 45 g of black pepper kernels. The samples were then heated in a 40.68 MHz RF field for 15 min. The population reduction of S. typhimurium in black pepper kernels was greater compared to E. faecium, indicating that E. faecium could exhibit higher heat resistance during RF heating and could be used a suitable surrogate for S. typhimurium during the sterilization process of black pepper kernels.