In this study, 100 samples of ice cream which were divided into 2 groups (50 vanilla and 50 chocolate) collected individually from different supermarkets in Mansoura city, Egypt, for sensory and bacteriological examination before subjection for radiation, then each group was divided into 2 subgroups and exposed to radiation. The 1st subgroup from the 2 groups was exposed to 2 KGy of gamma rays and the 2nd subgroup from the 2 groups was exposed to 3 KGy of gamma rays. After the radiation exposure, all the subgroups were subjected to sensory and bacteriological examinationto detectthe counts of aerobic plate bacteria; Staph. aureus; Bacillus cereus and coliforms. For the vanilla samples before radiation, the counts were 1.810~4 0.1410~2, 0.2810~2 0.09510~2, 2.210~2 0.410~2 and 1.610~2 0.0610~2 cfu/ ml respectively, and the counts after radiation in the 1st subgroup were 1.710~3 0.0310~2, 0.0610~2 0.0410~2, 0.610~2 0.1310~2 and 0.0610~2 0.02610~2 cfu/ml respectively, and in the 2nd subgroup were 0.710~2 0.0710~2, ND (not detected), 0.0810~2 0.0710~2 and ND cfu/ml respectively. For the chocolate samples before radiation, the counts were 3.810~4 0.2710~2; 0.510~2 0.0310~2; 0.810~2 0.1510~2 and 1.510~2 0.0710~2 cfu/ml respectively, and the counts after radiation in the 1st subgroup were 2.410~3 0.0410~2, ND, 0.1310~2 0.02510~2 and 0.0410~2 0.01710~2 cfu/ml respectively, and in the 2nd subgroup were 1.610~2 0.02610~2, ND, 0.0410~2 0.0110~2 and ND cfu/ml respectively. About the incidence of the isolated bacteria in the vanilla ice cream samples, E. coli, L. monocytogenes and Y. enterocoliticawere before the exposure to radiation in percentages as 12, 10 and 6 respectively, and in the chocolate samples were 10, 8 and 2 respectively. While, after the radiation exposure, non of E. coli, L. monocytogenes and Y. enterocolitica could be isolated from both the vanilla and chocolate samples. In addition, Salmonella typhimurium could not be isolated at all. Therefore, gamma irradiation can be applied at dose of 3 kGy to improve the microbial quality and safety of frozen ice cream products without adverse effects on human health and their sensory acceptability.
展开▼
