Structured lipids enriched with unsaturated fatty acids produced by enzymatic acidolysis of silkworm pupae oil using oleic acid: Enzymatic synthesis of structured lipid

Desilked silkworm (Bombyx mori L.) pupae oil has been identified as a valuable source of unsaturated fatty acids (UFAs). However, direct consumption is a food safety issue due to the presence of sn-1,3 triacylglycerols (TAGs), including palmitic acid (PA). A simple, selective and safe conversion to structured triacylglycerols (STAGs) with high UFA content is highly desirable. Novel STAGs with low PA and high α-linolenic acid (ALA), oleic acid (OA) and linoleic acid (LA) content were synthesized from silkworm pupae oil using a solvent-free system catalyzed by Lipozyme RM IM. Crystallization and melting profiles were determined using thermograms, and optimal conditions involved an enzyme load of 7%, a silkworm pupae oil TAG to OA molar ratio of 1:5, and a reaction temperature of 60°C. The content of PA and stearic acid decreased from 41.04 to 20.11%, while UFAs increased from 61.12 to 77.88%. The STAGs exhibited lower crystallization (−15.44°C) and melting (−23.47°C) profiles than TAGs (4.64 and −5.58°C, respectively). 1 Practical applications The presented methods using a solvent-free system enable STAGs to be synthesized using a natural substrate (desilked silkworm pupae oil). A simple, selective and safe conversion to STAGs with high UFA content and low PA content is highly desirable. This STAG is rare in nature and chemical synthesis is cumbersome. This STAG could be applied as a clinical treatment for nutritional enhancement with a beneficial effect on human health because of the high content of the ALA. Novel structure triacylglycerols (STAGs) with low palmitic acid and rich in oleic acid and linoleic acid were synthesized from silkworm pupae oil and oleic acid, through solvent-free enzymatic interesterification catalyzed by Lipozyme RM IM. Under the optimal conditions, the content of palmitic acid and stearic acid decreased from 41.04 to 20.11% in the sn-1, 3 positions, and the content of unsaturated fatty acids (including palm stearin, oleic acid, linoleic acid and α-linolenic acid) increased from 61.12 to 77.88%. The STAGs could be added into milk fat substitutes, which may be useful as nutrition enhancers for infants and may decrease obesity.