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KMID : 1160620040090040330
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Preventive Nutrition and Food Science
2004 Volume.9 No. 4 p.330 ~ p.335
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Effect of Heat Pretreatment on the Functional Constituents of Rice Germ
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Kwon Yun-Ju
Lee Ki-Teak
Yun Tae-Moon
Choi Sang-Won
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Abstract
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Changes in functional constituents of rice germ prepared using three different heat pretreatments: roasting, steaming and microwave heating, were determined and compared with those of non-treated rice germ. The yield of rice germ oil increased generally and then decreased with increasing time for all three heat pretreatments, although the yields of rice germ oil varied among the three heat pretreatments. There were no major differences in fatty acid compositions among the rice germ oils subjected to the three different heat pretreatments. Levels of α-tocopherol in rice germ oil increased up to about 1.5 times at 3 min of roasting and microwave heating, compared to control, and then decreased with increasing treatment time, but α- tocopherol concentrations in rice germ oil gradually decreased with increasing steaming time. The contents of three phytosterols (β-sitosterol, stigmasterol and ergosterol) decreased progressively with increases in roasting and steaming time, while concentrations of the three phytosterols increased up to ～15% with 3 min of microwave process as compared to control, and then decreased thereafter. Levels of γ-oryzanol in rice germ oil decreased gradually with increasing time during all three different heat pretreatments. However, levels of γ-aminobutyric acid (GABA) in rice germ decreased gradually with increasing roasting time, while those of GABA increased greatly up to about 2 times after 10 min of steaming process, and then decreased slowly thereafter. During microwave heating, the contents of GABA increased at 3 min of treatment time and then decreased. These results suggest that microwave heating may be the most suitable processing method to preserve functional constituents in rice germ.
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KEYWORD
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rice germ, functional constituents, roasting, steaming, microwave
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