Hummus (chickpea dip) is one of the most popular traditional foods in Middle East countries including Jordan. Recently, the incidence of pathogens and outbreaks associated with hummus has increased worldwide. Most common bacterial foodborne pathogens grow or survive in hummus are Salmonella, Escherichia coli and Listeria monocytogenes. Therefore, this study aimed to i) investigate the feasibility of using gamma radiation to eliminate Salmonella spp., L. monocytogenes and E. coli O157:H7 in hummus, ii) evaluate the effect of desiccation, heat stresses and cold on the sensitivity of these microbes toward irradiation. Hummus samples were inoculated with fresh or desiccated, heat, cold stressed cocktail cultures of Salmonella spp., L. monocytogenes or E. coli O157:H7 individually at level of ca 107 CFU/g and then exposed to gamma radiation at doses of. The populations of unstressed E. coli O157:H7, L. monocytogenes and Salmonella were reduced by 0.6-3.9, 1.0-3.0 and 0.7-2.9, respectively by 0-0.6 KGy of gamma irradiation. Desiccation, heat, cold and acid stresses prior irradiation treatment did not affect the resistance of E. coli O157:H7 toward gamma radiation. However, stressed L. monocytogenes and Salmonella cells were more resistant to gamma irradiation compared to control (unstressed) cells. This study approved the efficiency of low levels of gamma irradiation to reduce the risk of unstressed and desiccation, acid or heat stressed pathogens in hummus, although the environmental stresses enhanced the resistance of L. monocytogenes and Salmonella.
Amin N. Olaimat is an assistant professor of Food Safety and Hygiene at the Department of Clinical Nutrition and Dietetics, Faculty of Allied Health Sciences in the Hashemite University, Jordan. Olaimat completed his Ph.D. in Food Science from University of Manitoba, Canada and obtained his BSc. and Msc. degrees from the Jordan University of Science and Technology, Jordan. Olaimat has published 50 peer-reviewed papers in reputed international journals and 25 conferences beside 1 book chapter. His current research interests include the risk analysis and studying the microbial quality and safety of foods, development, use and evaluation of natural antimicrobials to enhance the safety and extend the shelf-life of foods, development of active packaging materials to improve the quality and safety of foods, and bacterial stress response in food environment and its impact on the irradiation and thermal inactivation of foodborne pathogens.