Microwave treatment improves shelf life of brown rice
2011
Bergonio, K.BN., Philippine Rice Research Inst., Maligaya, Science City of Munoz, Nueva Ecija (Philippines). Rice Chemistry and Food Science Div. | Lucatin, L.G.G. | Corpuz, G.A., Central Luzon State Univ., Science City of Munoz, Nueva Ecija (Philippines). Dept. of Chemistry | Aquino, D.V. | Duldulao, J.B.A., Philippine Rice Research Inst., Maligaya, Science City of Munoz, Nueva Ecija (Philippines). Rice Chemistry and Food Science Div.
Consumption of brown rice (BR), along with other whole grain cereals, has been intensively promoted for its high nutrient level and health promoting phytochemicals. However, one deterrent of its consumption is its short shelflife attributed to the lipid-rich layer on the grain which causes rancidity over time. This study sought to address this problem. BB was subjected to microwave treatment, at varied times (800 watts:30 sec, 60 sec and 90 sec) and stored up to six months and monitored every two months for changes in free fatty acid content, antioxidant activity, phenolic content, and sensory attributes. Relative to untreated sample, all treatments were found to effectively decrease lipase activity and consequently reduced free fatty acid released, even up to six months of storage. Longer microwave exposure resulted to lower free fatty acid generation during storage. Phenolic (soluble and bound form) content of treated and untreated samples were not significantly different, and tended to increase upon storage. Antioxidant activity increased significantly up to four months of storage. Such increase is presumably brought about by the increase in phenolic content. Initial raw and cooked rice sensory attributes of treated and untreated samples were comparable. By the second months slightly perceptible off-odor was noted in treated and untreated raw samples. Changes in glossiness and translucency in raw BR, while changes in glossiness and smoothness in cooked BR were also noted in all samples. Panelist found untreated BR unacceptable by the fourth month whereas microwave treated samples with 60 and 90 sec exposure were acceptable up to 6 months. Sixty sec was found to be most effective and economical in stabilizing brown rice against deterioration.
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