Microbial Populations, Sensory and Volatile Compounds Profiling of Local Cooked Rice

Abstract

This study is designed to investigate the microbial populations, sensory and volatile compounds profiling of locally cooked rice stored at room temperature (30 °C) on days 0, 1, 2 and 3 (D0, D1, D2 and D3) for the determination of its specific spoilage organisms (SSOs). Microbiological analysis showed the presence of spore-forming bacteria, yeast and moulds, which survived the cooking process. While Total Viable Count (TVC) exceeded the microbiological limit at 6.90 log CFU/g on D3, panellists deemed cooked rice unacceptable for consumption on D2 at a total sensory score of 11.00 which concludes D2 as the day cooked rice became spoiled. Through culture-dependent and culture-independent methods, Bacillus cereus was identified as the sole bacteria observed throughout the storage period confirming the bacteria as the SSO. The Volatile Organic Compounds (VOCs) analysis proposed several metabolites; 3-eicosene, 1-heptadecene, hexacosane, phenol, 4,4'-(1-methylethylidene)bis-, n-nonadecanol-1 and cyclohexanone as potential spoilage markers of cooked rice, that might be responsible for the off-odour produced by B. cereus during spoilage of cooked rice.