Separation of tocopherols and sterols from soy deodorizer distillate.

摘要

The process for the recovery of sterols and tocopherols from deodorizer distillate (DOD) was developed. It consisted of the recovery of sterols by crystallization, conversion of tocopherols to their succinates, and followed by crystallization to recover tocopheryl succinates thus formed. To recover sterols, esterification and/or transesterification followed by crystallization at room temperature were carried out. However, much loss of tocopherols and squalene was observed.; Another scheme of process to recover sterols was also developed where crystallization was conducted with different solvents at various temperatures. Several solvents such as McOH, 90% EtOH, acetone, and mixtures of acetone and McOH with varied proportions, were examined for their effectiveness of separation. The sterol crystals formed were removed from the solution either by centrifugation at low temperature and filtration, or by membrane process. The best results were obtained by crystallization at −20°C for 24 hrs with solvent mixture of acetone and McOH (4:1, v/v), followed by centrifugation, filtration and washing steps. Over 90% of original tocopherols and squalene in DOD were recovered in filtrate fraction, respectively, while 80% of total sterols were retained in cake fraction.; The succinylation reaction was carried out at 140°C for 1 hr using potassium acetate as a catalyst. The conversion was significantly increased to over 90% by increasing the amount of succinic anhydride from 10% to 13% and that of the catalyst from 1.3% to 2%. Meanwhile, the free fatty acid (FFA) content was increased around 10% after the succinylation reaction.; Crystallization of tocopheryl succinates was conducted at −20°C for 24 hrs with different solvents, such as hexane, petroleum ether, and a mixture of acetone and McOH (4:1, v/v). The crystallization results showed the recoveries of tocopherol succinates in cake fractions were poor with all solvents tested, with less than 10% of original tocopherol succinates in raw material being crystallized under conditions used. Among the solvents tested, hexane was better for recovery of non-α-tocopherol succinates in the cake fraction. Furthermore, high proportions of FFA were co-crystallized along with tocopherol succinates for all solvents used, leading to tocopherol succinates contents in cake fractions lower than that in raw material.