On the Oxidation of Rice Lipid Fractions Extracted from the Whole Grain by Immersion

용매침지(溶媒浸漬)에 의하여 추출(抽出)된 쌀알의 유지획분(油脂劃分)의 산화(酸化)에 대(對)하여

  • Cheigh, Hong-Sik (Food Resources Laboratory, Korea Institute of Science and Technology) ;
  • Kwon, Tai-Wan (Food Resources Laboratory, Korea Institute of Science and Technology)
  • 최홍식 (한국과학기술연구소 식량자원연구실) ;
  • 권태완 (한국과학기술연구소 식량자원연구실)
  • Published : 1972.09.28

Abstract

Oxidative changes in the rice lipids under accelerated condition were studied by measuring the changes in weight gain, total carbonyl compound, malonaldehyde, and fatty acid composition. Rice lipids were prepared by extraction with either n-hexane or ethanol from polished rice grain and purified by Folch's method. The lipid preparations were either incubated in dark at $40^{\circ}C$ or irradiated with ultra-violet light for a period of 55 days. Weight gain by oxygen absorbed sharply increased within 3 days in the rice lipids under UV light irradiation. However, with the rice lipids at $40^{\circ}C$ incubation a moderate increase in weight was observed only after 45 days storage. Their induction periods were one day (hexane extracted, under UV light), 2 days (ethanol extracted, under UV light), 30 days (hexane extracted, at $40^{\circ}C$), and 40 days (ethanol extracted, at $40^{\circ}C$) respectively. Oxidative rancid odor appeared at the end of the induction period. Total carbonyl compound and malonaldehyde markedly increased within 7 days, and decreased in the rice lipids under ultra violet light irradiation, while at $40^{\circ}C$ incubation they were continued to increase slowly through out the storage. The hexane extracted lipid were less stable than ethanol extracted lipid on the basis of oxygen absorption, malonaldehyde and other carbonyl compound formation. With the hexane extracted lipid during 55 days incubation at $40^{\circ}C$, the contents of linoleic and linolenic acids decreased, while the oleic, stearic, and palmitic acids increased.

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