Spoilage after cooking of some rice varieties commonly consumed in Sri Lanka

Abstract

Rice once cooked is perishable. In the present study we investigated cooked rice spoilage of common rice varieties in Sri Lanka. The study was further extended to compare the effect of clay and aluminium pots on the cooked rice spoilage and to study the potential to put off cooked rice spoilage in the traditionally used botanicals rampe (Pandans latifolia), curry leaves (Murraya koenigii} and turmeric (Curcuma domestica). One Gram positive bacteria was isolated and identified as Bacillus cereus. In cooked rice, the total count of Gram positive bacteria increased with time while the total count of Gram negative bacteria decreased. When inoculated separately to sterilized rice, the Gram positive bacteria multiplied to a significantly greater number (p < 0.05) than did Gram negative bacteria. The total bacteria count of different rice varieties was not significantly different from each other. Rumpe and curry leaves reduced the total Gram positive bacteria count of rice significantly (p < 0.05) while turmeric did not. The total Gram positive bacteria count of rice cooked in aluminium pots was significantly lower (p < 0.05) compared to rice cooked in clay pots.

Key words: Rice spoilage, Gram positive bacteria, Bacillus cereus, anti­bacterial effect, Pandanus latifolia

Vidyodaya J. of Sci.. (2009) Vol. 14, pp 131-141