Control of Bacillus cereus Populations in Brown Rice by Use of Common Foodservice Cooling Methods

Large quantities of food are often prepared, cooled, and stored for future food service in schools and other foodservice settings. The United States Food and Drug Administration indicates that inadequate (slow) cooling contributes to outbreaks of foodborne illness. Brown rice is commonly prepared in school settings and, when subjected to slow cooling, presents a risk for Bacillus cereus growth. To investigate this risk, brown rice was portioned to 2- and 3-inch depths in pans before inoculation with heat-shocked B. cereus spores (104–105 spores/g). All pans were stored, either uncovered or covered with single or double layers of aluminum foil, in a 20°C commercial walk-in freezer or were situated in ice water baths inside a 4°C commercial walk-in refrigerator. B. cereus populations were enumerated at 0, 4, 8, 12, and 24 hours. Treatment*time (P = 0.0026) and product depth*time (P = 0.0268) were significant. Between 0 and 24 hours, B. cereus populations declined during storage in the freezer and refrigerator and at both depths of brown rice. Temperature data indicate four cooling treatment combinations satisfied FDA Food Code cooling criteria. The lack of cover type (P > 0.05) significance, combined with B. cereus population declines during cooling, indicates that each cooling technique controlled B. cereus outgrowth in brown rice.