Solvent-free lipase-catalyzed preparation of diglycerides from co-products of vegetable oil refining

Abstract

Co-products of vegetable oil refining such as a mixed deodorizer distillate resulting from the refining of various vegetable oils, a crude distillate resulting from the physical refining of coconut oil and commercial mixtures of distilled sunflower and coconut fatty acids were used as starting materials for the enzymatic preparation of diglycerides. Reaction conditions (temperature, pressure, molar ratio) for the formation of diglycerides by lipase-catalyzed esterification/transesterification were studied using the mixed deodorizer distillate and glycerol as starting materials. The best results were obtained with the immobilized lipase B from Candida antarctica (Novozym 435) in vacuo at 60 °C leading to moderate proportions (~52%) of diglycerides. The proportion of diglycerides increased when residual acylglycerides of the co-products of vegetable oil refining were hydrolyzed prior to esterification. Thus, the esterification of hydrolyzed co-products of vegetable oil refining with glycerol led to high formation (62-72%) of diglycerides. Short-path vacuum distillation of the esterification products yielded distillation residues containing from 70% to 94% diglycerides. The proportions of fatty acids and monoglycerides in the distilled residues were quite low (≤ 1% and 1 to 3.9%, respectively). Immobilized lipases from Rhizomucor miehei and Thermomyces lanuginosus were less active as esterification biocatalysts.