Effects of microwave pretreatment and media milling on free fatty acid and bioactive compounds in rice bran
Date Issued
2011
Date
2011
Author(s)
Huang, I-Ching
Abstract
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.
Subjects
rice bran
microwave
media milling
oryzanol
phytic acid
SDGs
Type
thesis
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