The production of rice-bran structured lipids

Autor: Chung-Ta Lee, 李忠達
Rok vydání: 2008
Druh dokumentu: 學位論文 ; thesis
Popis: 96
Rice bran is a by-product of rice milling, which is rich in lipids. This lipid contains a great amount of functional components, including γ-oryzanol, tocopherol, tocotrienol and phytosterol, which provide physiological functions of lowering blood triglycerides, increasing high density lipoproteins (HDL) and antioxidative activities. However, the high amount of unsaturated fatty acids in the lipid makes it unstable and easy to be oxidized. This study used lipase to catalyze the production of structured lipids (SLs), which would contain both medium-chain fatty acids and essential fatty acids, through interesterification of coconut oil and rice bran oil. Oils extracted with n-hexane from four cultivars of rice bran TK 8, TK 9, TNG 67 and TNG 71 were used. The ratio of rice bran oil and coconut oil was 1: 5 (v/v), and the reactions were carried out at room temperature; sampling was conducted at 0, 1, 2, 4, 12 and 24 hr of reaction; the products were analyzed using HPLC to monitor the reaction and the functional components afterwards. Results showed that the enzymatic reactions were close to equilibrium after 4 h. Among the four cultivars, TNG71 SLs contained the highest amount of γ-oryzanol (8.96±0.68 mg/g structured lipids) and α-tocopherol (120.72±2.63 μg/g structured lipids), while the refinement resulted in a loss of these ingredients. A large amount of TNG 71 SLs was produced. The fatty acid composition was that 46.60% C12：0, 18.79% C14：0, 10.30% C16：0, 16.50% C18：1 and 7.81% C18：2. About a half of the fatty acid was MCF (~48%) which is considered to be readily metabolized to produce energy rather than be stored in adipose tissue in human body; besides, this lipid could provide 8% essential fatty acid. After refining, the SLs were analyzed with oil properties and qualities: iodine, 25.07±2.36 (g I2/100 g); saponification value, 214.31±2.24 (mg KOH/g); peroxide value, 4.73±0.23 (meq/kg); TBA value, 5.64±0.22 (mg malonaldehyde/kg). Iodine value and saponification value of the SLs were between the values of coconut oil and rice bran oil. Rancimat was used to evaluate the oil oxidative stability. At 120 and 130°C the synthesized SLs were more stable than the rice bran oil with 2.3 and 3.4 times of stability, respectively.
Databáze: Networked Digital Library of Theses & Dissertations
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