MODELING THERMAL DESTRUCTION CHARACTERISTICS OF BACILLUS CEREUS IN SORHUM (Sorghum bicolor L. MOENCH) STARCH

This study evaluated the thermal destruction characteristics of Bacillus cereus in sorghum starch as to enhance its microbiological safety. Mature sorghum grains were sourced and processed into starch under hygienic conditions. The extracted starch was dried, inoculated with B. cereus and subjected to thermal treatments. Design Expert 13 for Windows was used for experimental lay-out interactive effect comprising temperatures (80 - 90 ℃) and water activity (aw) (0.4 - 0.8) and all experiments were conducted in triplicate. Thermal destruction characteristics of Bacillus cereus in sorghum was obtained by plotting number of survivor (CFU/g) against time and corresponding thermobacteriological parameters were obtained. Other thermobacteriological parameters: z-value, F-value and activation energy were obtained using appropriate equations. The thermal death time data (D-value) obtained were fitted into model using Design Expert 13 for Windows. Thermal parameters such as D-value, k-value, F-value, z-value and activation energy (Ea) values ranged from 60 - 108 min; 156 – 205 min; 48.32 – 62.11 °C and 39.457 – 66.765 kJ/mol, respectively. The results indicated that Bacillus cereus in sorghum starch showed significant inactivation at temperature, 90 ℃ and 0.4 aw. The result obtained showed that the D-value of B. cereus in sorghum starch as influenced by inactivation temperature and aw had quadratic effect. This study provided valuable thermal destruction characteristics data that could be employed as a guide to potential food processors, scientists and engineers in order to improve consumption safety of the product.