Separation Of Tocopherols, Sterols And Fatty Acids From Soybean Oil Deodorizer Distillate

In order to recovering fatty acids, sterols and tocopherols from soybean oil deoeorizer distillate (DOD), various aspects of the traditional process such as esterification/transesterification reactions, crystallization and high-vacuum distillation have been studied. On this base, a new process was developed.As for the esterification/transesterification reactions, when the soybean oil deodorizer distillate is esterified with 84%wt methanol at 65℃in the presence of 2%wt concentrated sulphuric acid, the optimum reaction time is 2h, and the conversion can be up to 98.49%. When the esterification product is transesterified with 58.5%wt methanol at 65℃using 1%wt KOH as a catalyst, the optimum reaction time is 1h. If the fatty acid methyl ester is removed by roto-evaporation under high vacuum and high temperature after esterification reaction, the conversion of transesterification reaction can be greatly enhanced.Crystallization of sterols with the solvent mixture of acetone and methanol has been studied. The results indicate that, compared with crystallization of sterols from DOD, the purity of sterols obtained by crystallization from esterified DOD is higher, but the yield is lower. There is no distinct difference between the compositions of the two sterol products, which means the esterification/transesterification reactions have nothing to do with the composition of sterols. Considering the increasion of the proportions of campersterol and stigmasterol, the solvent mixture of acetone and methanol has some effects on the enrichment of these two sterols.Esterified DOD,DOD without sterols,esterified DOD without sterols are distilled under high vacuum respectively. The results show that high-vacuum distillation of DOD without esterification demands higher operating temperature and larger energy consumption, but the yield and the purity of the fatty acid are acceptable, and the fatty acid products can be directly obtained economically and feasibly by omitting hydrolysis of the fatty acid methyl ester. Removing sterols before high-vacuum distillation can improve the yield of fatty acid methyl ester.According to the above experiment results and the deficiency of the traditional process, a new process was developed for efficiently recovering tocopherols, sterols and fatty acids from DOD. Sterols present in DOD are separated by crystallization, and then the fatty acids are distilled off under high vacuum. Tocopherols can be extracted from the residue. Starting with DOD, a recovery of fatty acids as high as 93.54% was achieved by the new process, the sterols are successfully purified with the yield 85.35% and the purity 77.1%, and tocopherols are isolated with the yield 47.07% and the purity 68.4%. Compared with the traditional process, the new process is more economical and effective.