Enzymatic synthesis and characterization of MLM-type structured lipid using grapeseed oil and capric acid

The objective is to optimize the reaction conditions for high C10:0 incorporation into grapeseed (GS) oil, and to study the changes in antioxidant activity and functionality of its structured lipid (SL) product. Taguchi method was used to optimize C10:0 incorporation by combining parameters in a total of 9 experiments. C10:0 incorporation and triacylglycerol (TAG) species of the SL were analyzed for the 9 samples to determine optimal conditions and enzyme type for scaled-up (300 g) SL synthesis. Scaled-up SL was purified using short path distillation and fully characterized in terms of lipid classes, tocopherol, thermal behavior, and oxidative stability. Lipozyme® RM IM (Rhizomucor miehei immobilized lipase) and Lipozyme® 435 (Candida antarctica recombinant immobilized lipase) were used to determine which enzyme produced higher C10:0 incorporation. The optimal conditions were the same for both enzymes as follows: substrate molar ratio 1:3 (GS oil: C10:0), enzyme load 5% (w/w) of substrates, temperature 65 ℃, and time 12 h. SL synthesized using Lipozyme® RM IM had MLM-type TAG species of 11.51 ± 0.11 mol% and SL synthesized using Lipozyme® 435 had 12.68 ± 0.34 mol%. The C10:0 incorporation in the SL using Lipozyme® RM IM was 46.03 ± 0.55 mol%, while Lipozyme® 435 incorporated 47.28 ± 1.22 mol% and they were not significantly different. However, the total C10:0 incorporated into TAG species for Lipozyme® RM IM was significantly higher (60.08 ± 0.04 mol%) compared to 50.78 ± 0.44 mol% for Lipozyme® 435.
Scaled-up acidolysis reaction and characterization were done on SL synthesized using Lipozyme® RM IM. The yield of purified scaled-up SL after short path distillation (SPD) was 72.96 wt%. The antioxidant in SL was reduced after SPD due to loss of tocopherols. This MLM-type-SL has a high incorporation of C10:0 at a relatively lower reaction time, and may have functional and health benefits.