Inhibiting the growth of Bacillus cereus in raw sprouts and cooked rice using red clover seeds
Khalid, Mahmoud F.
Internet Journal of Food Safety
The growth of enterotoxigenic Bacillus cereus in perishable foods is a well-known cause of food poisoning. In this study, we evaluated sprouting seeds (broccoli, green peas, lentil, mung bean, mustard, radish, red clover, soybean, and triticale) for their antimicrobial activity toward B. cereus. The filter-sterilized seed extracts of red clover, lentil, and mung bean yielded inhibition zones of 11.7, 9.2, 8.3 mm, respectively. However, no significant inhibition (≤ 6 mm) was observed with other seed extracts. Naturally occurring B. cereus multiplied from 1.1 to near 5.0 log CFU/g during broccoli and radish sprouting. In contrast, B. cereus growth was suppressed when brassica and red clover seeds were grown together. A mixture of seeds containing 10% red clover reduced B. cereus counts to ≤ 1 log CFU/g at the end of sprouting. Artificially inoculated B. cereus (1.1 log CFU/g) grew to 5.9 and 5.6 log CFU/g in white and black rice, respectively, during storage for 24 h at 24oC. Adding a small amount of red clover seed extract (2.5 ml per 25 g of cooked rice) reduced the respective growth by 3.2 and 2.3 log CFU/g. B. cereus counts on the treated white and black rice were about 4.9 and 3.7 log CFU/g, respectively, after 48 h of storage at 24oC. In conclusion, the antimicrobial activity of some legume seeds has potential to be utilized to inhibit B. cereus in food systems.