Lipids from rice bran (Indica type Milyang # 23), both fresh and stored at 30℃ and 80% relative humidity for 5 weeks, were separated and analyzed for the determination and the storage effect on the bran lipid composition.
Total lipids of fresh rice bran consisted of 89.9% neutral lipids, 8.0% glycolipids, 2.1% phospholipids and no significant changes of these fractions were noted during storage. Triglycerides(43.1%), diglycerides(13.8%) and hydrocarbon-esterified sterol(13.5%) among six fractions were considered as main components in neutral lipids. After storage triglycerides content significantly decreased as the free fatty acid increased in the neutral lipid fraction. Major components of the glycolipid fraction were acylsterolglycoside(43.1%) and sterolglycoside(30.3%). Phosphatidyl choline(39.8%), phosphatidyl serine(20.9%) and phosphatidyl ethanolamine(19.8%) were predominent in the phospholipid fraction. No significant changes of the composition were shown in fraction of the glycolipid or the phospholipid during the storage period.
Major fatty acids of the total lipid fraction were oleic(44.3%), linoleic(32.5%) and palmitic acids(18.4%). The fatty acid compositions of the neutral lipid, the glycolipid and the phospholipid fractions were similar to the total lipid fraction. Small changes in fatty acid composition in each fraction were noted during the storage period. The acid value increased but iodine value decreased during the storage period. The values of peroxide and TBA increased gradually in the first three weeks, and then slowly decreased in the fourth and the fifth week of the storage.
|