full2010.pdf - page 1227

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Abstract
An investigation into the effects of extraction temperature (30 50 and 70 oC) and extraction time (30 45
and 60 min) on total phenolic content, DPPH-radical scavenging activity and reducing power of the ethanolic
extracts from three types of Sang Yod rice bran. The results showed the ethanolic extracts from raw Sang Yod rice
bran, Sang Yod rice bran defatted with hexane and Sang Yod rice bran defatted with screw press at the extraction
temperature of 30 oC and extraction time of 60 min had the highest total phenolic content of 6.28 5.57 and 2.59
ôg gallic acid/mg extract, respectively. Meanwhile, the ethanolic extracts from Sang Yod rice bran defatted with
hexane possessed the highest DPPH-radical scavenging activity (63.24 %) and reducing power (0.260) at the
extraction temperature of 30 oC and extraction time of 60 min. However, the total phenolic content, DPPH-radical
scavenging activity and reducing power of all ethanolic extracts from Sang Yod rice bran increased with an
increase extraction time, but decreased at the higher temperature. In addition, the effect of heat treatment (100 oC
for 15 and 30 min) and pH (4 7 and 9) on the stability of antioxidant properties of all ethanolic extract from Sang
Yod rice bran were investigated. The DPPH-radical scavenging activity and reducing power of all ethanolic
extracts from Sang Yod rice bran remained constant when incubated at 100 oC for 30 min. For pH stability,
DPPH-radical scavenging activity and reducing power of all ethanolic extracts from Sang-Yod rice bran were
higher at pH 4 than pH 7 and 9.
Keywords: Rice bran, Extraction, Total phenolic content, Antioxidant activity
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