88D-10 |
Effects of storage conditions on yeast and mold and total aerobic bacterial counts on stored rice. |
R. P. RANALLI and T. A. Howell, Jr. Food Science, University of Arkansas, 2650 N. Young Avenue, Fayettville, AR 72704 With increasing demands for rice processors to meet microbial specifications and increasing evidence that changes caused by microflora on rice enhance deterioration in rice quality, it is important to understand how storage conditions will influence these counts on rice. Our objective was to determine the effects of storage conditions on yeast and mold and total plate counts in stored rough rice. Rice (cv.Cypress) harvested in late August, 2000 in Grady, AR was dried to approximately 13% moisture content (wet-basis) and placed in six 28,000 bu bins (each bin was filled with ~21,000 bu). Three bins were equipped with an aeration control system that aerated the rice at specific ambient air conditions. Three bins were aerated manually by the on-site grain drying manager according to traditional practice. Rice was sampled from the north (N), south (S), and central (C) positions in each bin at a depth of approximately 1 m. After sample collection, 10g of each component sample was diluted, masticated and plated on 3M APC/Yeast and Mold Petri-Film (Minneapolis, MN) in accordance with AOAC methods 990.12 and 997.02, respectively. This process was repeated monthly for four months of storage. Results indicate that both the yeast and mold counts and total aerobic plate counts decreased as the storage duration increased and as the temperature of the rice decreased. An average initial decrease of 0.3 log colony forming units per gram per month (CFU/g/mo) on total plate counts and 0.6 log CFU/g/mo on yeast and mold counts were found. Rice in manually aerated bins had lower microflora counts over the storage period than the rice in the thermostatically controlled bins. Rice storage managers can take measures to reduce total aerobic plate counts and yeast and mold counts so that rice processors can reach desired microbial specifications and decrease deterioration caused by yeast and mold.
Session 88D, Food Microbiology: General
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