Effect of Gamma Radiation on Escherichia coli, Salmonella enterica Typhimurium and Aspergillus niger in Peppers

Introduction: Chili pepper (Capsicum frutescens L. var. conoides Bailey) and Sichuan pepper  (Zanthoxylum bungeanum Maxim.) are important spices which extensively used as natural flavor in food, and they are especially in great demand in traditional Chinese cuisine. They were mixed with other spices, and added directly into many Ready-to-Eat foods. However, these spices are highly susceptible to microbial contamination in the process of growing, harvesting, processing and transporting, etc.

Purpose: The objective of this study was to examine the effect of gamma irradiation dose for inactivating pathogens including E. coli, Salmonella Typhimurium and A. niger inoculated in dried chili pepper and dried Sichuan pepper and to evaluate the sufficient dosages among different samples and pathogens.

Methods: Two widely used spices, Chili pepper and Sichuan pepper inoculated with Escherichia coli, Salmonella enterica Typhimurium and Aspergillus niger were irradiated with gamma ray. The efficacy of irradiation to inactivate pathogens was investigated.

Results: The results showed that irradiation at doses 4.00 kGy and 5.00 kGy was appropriate for eliminating almost all E. coli and Salmonella Typhimurium in two peppers, respectively. A. niger was undetectable in chili and Sichuan pepper at doses 1.50 kGy and 1.00 kGy radiation. The D₁₀-values of E. coli, Salmonella Typhimurium and A. niger in Sichuan pepper were 0.81, 0.93 and 0.20 kGy, and 0.82, 0.69 and 0.49kGy in chili pepper.

Significance: Low levels of radiation by gamma ray can assure the inactivation of E. coli, Salmonella and A. niger in peppers, which makes for a safer product for the consumer. The irradiation at appropriate doses is a promising approach for producing safe and pathogen-free peppers for consumers.