Inactivation of Escherichia coli O157: H7 and Salmonella Typhimurium in black pepper and red pepper by gamma irradiation

This study evaluated the efficacy of gamma irradiation to inactivate foodborne pathogens in black pepper (Piper nigrum) and red pepper (dried Capsicum annuum). Black pepper and red pepper inoculated with Escherichia coli O157:H7 and Salmonella Typhimurium were subjected to gamma irradiation in the range of 0, 1, 2, 3 and 5kGy, and color change was evaluated after treatment. Pathogen populations decreased with increasing treatment doses. A gamma irradiation dose of 5kGy decreased E. coli O157:H7 and S. Typhimurium populations >4.4 to >5.2logCFU/g in black pepper without causing color change. Similarly, 5kGy of gamma irradiation yielded reduction of 3.8 to >5.2logCFU/g for E. coli O157:H7 and S. Typhimurium in red pepper. During gamma irradiation treatment, L^*, a^* and b^* values of red pepper were not significantly changed except for 297μm to 420μm size red pepper treated with 5kGy of gamma irradiation. Based on the D-value of pathogens in black pepper and red pepper, S. Typhimurium showed more resistant to gamma irradiation than did E. coli O157:H7. These results show that gamma irradiation has potential as a non-thermal process for inactivating foodborne pathogens in spices with minimal color changes.