| With shea olein as raw material, low acid value shea olein was obtained by methyl esterification, then triglyceride was transformed into fatty acid methyl ester by transesterification. After the fatty acid methyl ester and bioactive compounds were separated into light fraction and heavy fraction by molecular distillation, the heavy fraction (bioactive compounds) was crystallized with solvent to further improve the content of active compounds.The optimal methyl esterification conditions were determined by single factor experiment as follows: reaction temperature 70 ℃, reaction time 3 h, mass ratio of methanol to oil 3∶10, dosage of concentrated sulfuric acid 3%. Under these conditions, acid value of shea olein reduced from 56.1 mgKOH/g to 2.1 mgKOH/g, and the conversion rate of free fatty acids reached 96.3%. The optimal conditions of molecular distillation were obtained by single factor experiment as follows: feed rate 2 mL/min, scraper speed 250 r/min, distillation temperature 150 ℃, vacuum degree 0.1 Pa. Under these conditions, the recovery of the bioactive compounds in heavy fraction was 95.9% and the content of bioactive compounds was up to 68.8%. By the methods of methyl esterification, transesterification, molecular distillation and crystallization, the total content of triterpene and sterol in the product could reach 69.80%, and the content of bioactive compounds could achieve 83.18%. |
