Radiation sensitivity of selected pathogens in ice cream

Abstract

Microbial contamination was investigated using ice creams with a vanilla, chocolate, and strawberry flavor commercially available in Korea. Radiation sensitivity of the food-borne pathogens was also determined by an inoculation test. Food-borne pathogens used were Listeria ivanovii, Escherichia coli, and Salmonella typhimurium. Total aerobic bacteria, moulds and yeasts, and coliforms in the ice creams ranged from 2 to 3 log CFU/g. Irradiation of 3 kGy was enough to inactivate the total aerobic bacteria for the vanilla ice cream but that of 5 kGy was needed for the chocolate or strawberry ice creams at a frozen condition (-20 degrees C). To inactivate (> log 6.5) the inoculated L. ivanovii, E coli, and S. typhimurium into ice cream irradiation of 3, 1, and 0.1 kGy was needed, respectively. The D-10 value of L. ivanovii and E coli was calculated as 0.71-0.77 and 0.28-0.38 kGy range for the ice cream with different flavors at -72 degrees C, respectively. The D-10 value of S. typhimurium could not be calculated in this study because even 0.1 kGy of irradiation reduced the number of S. typhimurium to undetected level. Results suggest that a low dose irradiation can improve the microbial quality and reduce the risk by the food-borne pathogens of ice cream, which has limited alternative sterilization methods due to the temperature characteristics of the products. (c) 2006 Elsevier Ltd. All rights reserved.