Lipase-catalyzed acidolysis of walnut oil as a green strategy to synthesize structured lipids rich in α-linolenic acid: Preparation and characterization

The growing interest in n-3 polyunsaturated fatty acid (n-3 PUFA) concentrates is driven by their well-documented health benefits and promising applications in the food industry. Walnut oil (WO) generally contains low levels of n-3 PUFAs, which restricts its market potential. This study aimed to incorporate α-linolenic acid (ALA) into walnut ( Juglans regia L.) oil (WO) via lipase-catalyzed acidolysis. The catalytic efficiency of three immobilized lipases (Lipozyme RM IM, TL IM, and Novozym 435) for ALA-SL synthesis was compared, with Novozym 435 exhibiting the highest activity over a 38-hour reaction period. The optimal reaction conditions for ALA-enriched structured lipids (ALA-SLs) production were optimized via response surface methodology (RSM): a reaction temperature of 54.8 ℃, a substrate molar ratio (ALA/WO) of 2.65, and an enzyme load of 7.65 % (w/w). Following purification via molecular distillation, the overall ALA inserted rate in ALA-SLs reached 20.56 %, with a specific inserted rate of 10.43 % at the sn-2 position. A total of 33 triacylglycerols (TAGs) were identified, with 75.35 % containing ALA. Thus, ALA-enriched TAGs were successfully synthesized. In conclusion, this study successfully developed ALA-SLs with favorable thermal stability and oxidation resistance, providing a valuable theoretical basis and technical support for expanding the diversity and commercial value of walnut oil-based products. • Lipase-catalyzed acidolysis of WO served as a green strategy to synthesize ALA-SLs. • The optimal synthetic parameters of ALA-SLs were fixed by RSM. • The physicochemical properties of ALA-SLs were similar to WO.