Abstract: Coconut oil is limited in its application in the food industry due to its high saturated fatty acid content and high freezing point. Meanwhile, the impact of specificity differences among various lipases on the modification effect of coconut oil remains unclear. In this study, four lipases were employed for the hydrolytic modification of coconut oil. The changes in lipid composition, physicochemical properties, and antibacterial activity after modification were determined, and the regulatory mechanism of lipase specificity on the modification effect was investigated. The results showed that the relative content of lauric acid in coconut oil glycerides was (50.37 ± 0.17)%, which decreased to (34.69 ± 0.04)% and (36.89 ± 0.11)%, respectively after enzymatic hydrolysis with MHA “Amano” 10SD (10SD) and Lipozyme® TLIM, while that of unsaturated fatty acids increased correspondingly. The relative content of diglycerides in the 10SD-treated group reached 59.81%, and its sliding melting point was 22.3 ℃, lower than that of the untreated control (28.2 ℃), indicating transition from a solid to a liquid state at room temperature. Antibacterial assays revealed that coconut oil exhibited no inhibitory effect on Escherichia coli, whereas 10SD-hydrolyzed coconut oil showed the strongest antibacterial activity, with an inhibition zone diameter of (12.96 ± 0.48) mm against E. coli. This study clarified the regulatory effect of the hydrolytic specificity of different lipases in the lipid composition and antibacterial properties of modified coconut oil. The lipase 10SD demonstrated a substrate preference for medium-chain saturated fatty acids, and its hydrolysis produced lauric acid derivatives with antibacterial effects. These findings provide solid data support for expanded application of modified coconut oil in the food and pharmaceutical fields.

Key words: coconut oil; enzymatic hydrolysis; lipid composition; antimicrobial properties