Synthesis and characterization of medium- and long-chain structural lipid rich in α-linolenic acid and lauric acid

Abstract

Medium- and long-chain triglycerides (MLCT) have been widely concerned. In this study, lauric acid (La) was incorporated into flaxseed (Linum usitatissimum L.) oil (FO, aLna-riched) by lipase-catalyzed acidolysis. The synthesis efficiency of four immobilized lipases (Lipozyme RM IM, TL IM, AOAB8 and Novozym 435) was compared, while Lipozyme AOAB8 reaction for 2 h was the best scheme. Further, the optimal conditions for synthesizing structural lipids (aLSLs, rich in aLna and La) were obtained by response surface methodology: the reaction temperature was 44.6 °C, substrate molar ratio was 12 (La/FO), and enzyme loading was 9.11%. After purification by molecular distillation, the triglycerides (TAGs) of aLSLs contained 75.35% of TAGs with α-linolenic acid (aLna), 40.82% of MLCTs with La, and 26.75% (65.53% of the total MLCTs) of TAGs with both aLna and La (ɑ-MLCT). Meanwhile, the content of La and aLna in aLSLs were 22.38% and 39.78%, respectively. The chemical structure and microstructure of aLSLs were similar to FO. In addition, the thermo-oxidative decomposition behavior of aLSLs was significantly improved compared with physical mixture oil. This improvement might be related to the insertion of La and the structure of TAG. In all, this study firstly developed a novel thermo-oxidatively stable MLCT with high levels of aLna and La.