Antimicrobial effect of some natural oils on Bacillus cereus in minced beef

Abstract

A total of 1800 g fresh minced beef were divided into 6 equal groups (3x100 g of each). Bacilluscereus was inoculated into each group with infective dose 29x107 cfu/g. The used natural oils werethyme oil (0.6% and 1%), cinnamon oil (0.6% and 1%) and mixture of them (0.4 % from each). Theinoculated samples were stored at 4oC in refrigerator until be used. The inoculated groups wereexamined every 24 hours for sensory examination (overall acceptability) and B. cereus count. Theexperiment was performed in triplicate. Thyme oil (0.6 and 1%) decreased count of B. cereus(cfu/g) from 2.2x108(initial load) to 5.8x107and 8.8 x106with reduction percentages 73.63% and96% on 5th day and 6th day of storage, respectively. Cinnamon oil (0.6 and 1 %) decreased count ofB. cereus (cfu/g) to 9.8x107 and 6.1 x107 with reduction percentages 55.45% and 72.27% on 3rd dayand 5th day of storage, respectively. Mixture of (thyme and cinnamon oils) decreased count of B.cereus (cfu/g) to 8.6x106 with reduction percentage 96.09% on 6th day of storage. In control group B.cereus count increased from 2.2x108 (initial load) to 5.1x108 on 3rd day. Furthermore, thyme oil(1%) and mixture treated minced beef showed overall acceptability till 6th day of storage. Incomparison, thyme oil (0.6%) and cinnamon oil (1%) showed overall acceptability till 5th day.While, cinnamon oil (0.6%) and control group showed overall acceptability till 3rd day. Generally,mixture of thyme and cinnamon oils (0.4% of each) proved to be more efficient than otherconcentrations in suppression of B. cereus growth in minced beef, Therefore, It is recommended toimprove safety of the meat products.