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Quality Preservation of Moist Paddy Under Hermetic Conditions

J.E. DONAHAYE,1* S. NAVARRO,¹ S. ANDALES,² ANGELITA M. DEL MUNDO,³ FILIPINAS CALIBOSO,² GLORY SABIO² ANGELINA FELIX³, MIRIAM RINDNER,¹ A. AZRIELI¹ and R. DIAS¹

¹Department of Stored Products, Agricultural Research Organization, The Volcani Center, Bet Dagan 50250, Israel [* e-mail: jondon@netvision.net.il]
²Bureau of Postharvest for Research and Extension (BPRE), CLSU Compound, Nueva Ecija, Philippines
³ Institute of Human Nutrition and Food, College of Human Ecology, University of the Philippines, Los Banos, Laguna, Philippines

Abstract: Two laboratory studies were carried out to evaluate the influence of hermetic storage on the quality conservation of paddy at different water activities. Five moisture content (M.C.) levels of paddy were used, namely, 14, 15, 16, 17 and 18% w.b., approximately corresponding to the following water activities: 0.75, 0.80, 0.85, 0.88 and 0.90 aw. Quality evaluations were carried out after five storage periods, namely: 0, 1, 2, 3, 4 weeks for the first experiment and seven storage periods, namely 0, 1, 2, 3, 4, 5, 6 months for the second experiment. The entire study was undertaken at room temperatures of ~ 29º to 30ºC prevailing in the Philippines. Cooked rice aroma, taste, tenderness, cohesiveness, color and gloss were found to be negatively correlated with moisture content (m.c.) and storage duration of the paddy. The poor acceptability and preference-scores for cooked milled rice samples from paddy stored hermetically at 16% to 18% m.c. was primarily dictated by the presence of fermented smell in these samples. In the raw form, wholeness of grains and color were found to have a significant negative correlation with m.c. and storage duration. Analysis of microfloral loads and bacteria revealed an increase in bacterial counts for the paddy held at 17% and 18% m.c.

Field trials using sealed flexible storage structures of 10 tons capacity were undertaken. It was clearly demonstrated that the rates of oxygen depletion in hermetically sealed 18% m.c. paddy could prevent mold proliferation. The effects of hermetic storage upon paddy quality were also evaluated using cooking and acceptability parameters obtained after 1, 3 and 6 months of storage. The findings indicated that after 1 month, quality of sealed paddy stored at 18% m.c. had not deteriorated perceptibly. However, further evaluations made on paddy stored hermetically for 1, 3 and 6 months under both laboratory and field conditions confirmed that after the first month of storage the quality of moist paddy (16-18% m.c.) deteriorated progressively and the grain was no longer acceptable to the taste panels.

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