Abstract
ABSTRACTThe effect of ozonation as a method to reduce Bacillus cereus count in processed rice was investigated. Hundred grams of processed rice was exposed to gaseous ozone in an inert glass condenser at 20 ± 3C and 50% relative humidity. Ozone concentrations of 0.1, 0.2, 0.3 and 0.4 ppm up to 7 h were used. Enumerations of B. cereus were done before ozonation treatment to establish the initial counts of B. cereus in processed rice. The experiments were done in an air‐conditioned room and samples were then kept at ambient temperature pre‐ and post‐ozonation to emulate normal conditions in rice storage facilities. Within 24 h, the ozonated samples were then enumerated by surface spread plating technique. Significant trends were observed in comparison with the non‐ozonated rice samples. Non‐ozonated rice samples were found with an average of 5.50 ± 0.28 log count (cfu/g). Up to 1.63 log reductions of B. cereus counts were observed above 0.3 ppm ozone concentration at the end of 420 min of treatment. B. cereus counts were shown to decrease to 3.62 ± 0.38 log count (cfu/g) at 0.4 ppm ozone concentration for 420 min of ozone treatment.PRACTICAL APPLICATIONSUncooked rice grains are frequently contaminated with Bacillus cereus spores, which are resistant to heat and can survive boiling. If cooked rice is subsequently stored at room temperatures for an amount of time, the heat‐resistant spores will germinate, proliferate and may produce emetic toxin. No official information is available on the incidence of B. cereus poisoning in Malaysia but rice poisoning was often headlined as the main cause of foodborne illness. The aim of this study is to inactivate B. cereus count in raw rice, subsequently in cooked rice, and to prolong the shelf life of cooked rice. Ozone, with its antimicrobial properties and the ability to effectively kill 90% of microbial counts, was used at its highest advantage to minimize the B. cereus counts in processed rice.
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