Effects of microwave pretreatment and media milling on free fatty acid and bioactive compounds in rice bran
|Keywords:||米糠;介質研磨;微波加熱;米糠醇;植酸;rice bran;microwave;media milling;oryzanol;phytic acid||Issue Date:||2011||Abstract:||
米糠為碾米過程的副產物，由於脂解酶(lipase)等酵素的作用容易酸敗，不利儲存與應用，且顆粒大，適口性差，不易被消費者接受。但米糠中含有豐富的膳食纖維與抗氧化物質，如：阿魏酸(ferulic acid)與米糠醇(gamma-oryzanol)等，可降低心血管疾病及癌症發生率。本研究目的為利用微波前處理降低米糠中游離脂肪酸的生成，並探討介質研磨對米糠中游離脂肪酸與機能性成份的影響。結果顯示，微波處理(2450 MHz，800 W，2.5分鐘)的米糠於25℃下儲藏14週與原料相比，可有效降低90.3%的游離脂肪酸生成量，相同水分含量時(4.7
Rice bran is a byproduct of the milling process for making polished rice. Rice bran has short shelf life due to formation of free fatty acids (FFA) because of lipases. Another issue is the gritty texture of product which diminish consumers acceptance. Nevertheless, rice bran consists of dietary fiber, as well as antioxidants such as phenolic acid and gamma-oryzanol, both have been shown to reduce the risk of coronary heart disease and cancer. The objective of this study was to prepare ultrafine rice bran particles with extended shelf life and smoother texture by combining microwave and media milling. The bioactive compounds were also determined. Microwave reduced 90.3% of FFA during 14-week storage at 25°C. The data confirmed that microwave effectively inhibited the formation of FFA. After media milling, the volume mean diameter decreased from 297 micrometer to 12 micrometer and there were 80% particles smaller than 25 micrometer. Milled rice bran suspensions had good stability for 6 hours, smoother texture and with no precipitation occurred. Microwave was helpful for stabilizing gamma-oryzanol during storage and didn’t result in the loss of gamma-oryzanol. The extracted amount of gamma-oryzanol was increased by 10% after milling. In the antioxidant assay, milled rice bran had better DPPH scavenging activity and reducing power compared to unmilled rice bran, using the same amount of sample. The extractability of phytic acid wasn’t affected by microwave heating but media milling decreased the extracted amount by 6%. Rice bran after milling may result in phytic acid binding to components of rice bran suspension easier, thus reduce the extractability of milled rice bran. A rice bran suspension which had good stability, smoother texture and high value of nutrients was produced by combining microwave and media milling.
|Appears in Collections:||食品科技研究所|
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