Research On Synthesis Of Phytosterols α-Linolenate By Catalysis Of Lipase

Plant sterol andα-linolenic both possessed activities of hypolipidemic activity and preventing cardiovascular diseases.However poor solubility of plant sterol in lipid and oxidation instability ofα-linolenic limited their application in food industry, which could be improved by converting the two compounds into phytosterolsα-linolenate.Phytosterolsα-linolenate with high security could be obtained by lipase catalyzing esterification in gentle condition,but there were no reports on the research. In the paper,researches including synthesis of phytosterolsα-linolenate by lipase catalysis,physical and chemical properties,and structure of product were carried out.The main conclusions were obtained as follows:1.Synthesis technology of phytosterolsα-linolenate by lipase catalysisWe studied factors affecting esterification rate by single factor and orthogonal test,results showed that effect of temperature was the greatest,followed by substrate ratio and enzyme addition.Finally,we got the appropriate esterification conditions as follows:Novozyme 435 addition was 5%,mixed solvent proportion(iso-octane: hexane:cyclohexane) was 6:2:2(v/v/v),solvent and substrate ratio was 1.6:1 (ml/g),temperature was 55℃,and substrate ratio(α-linolenic:phytosterol) was 3:1. In the conditions,the esterification rate reached to 40.56%and finally to 75%by purification.2.Structure of phytosterolsα-linolenateMain ingredient in the products was confirmed as phytosterolsα-linolenate by TLC,FTIR,UV-VIS and NMR.Results showed that there were no organic acid,aldehyde and free hydroxyl existed in the product,and formation of ester bond was observed.The content of trans fatty acid in product was less than 0.1%by GC-MS.3.Physical and chemical characteristics of phytosterolα-linolenateFat-solubility of plant sterol was increased by 20-30 times in plant oils after etserification.Inductive time of ethylα-linolenate was 15.46h and phytosterolsα-linolenate were 15.46h and 2.93h respectively,but phytosterolsα-linolenate made oxidation stability of plant oil decreased,which were observed by using Schaal-oven method and Rancimat instruments.Crystallization behavior was studied by DSC, crystallization temperature of phytosterolsα-linolenate was -25.9℃--29.6℃,and phytosterolsα-linolenate made the crystallization temperature of plant oil decreased 6℃-10℃.