Enzymatic Conversion of Camellia Seed Oil into Glycerol Esters: Synthesis, Characterization, and Mechanistic Analysis

The conversion of triglycerides in edible oils into diacylglycerols (DAGs) is of great significance for obtaining products with health benefits. Camellia seed oil (C-oil), which is rich in oleic acid and linoleic acid, is an excellent raw material for the production of DAGs. In this study, the hydrolysis rate reached 87.14% under optimal hydrolysis conditions (reaction temperature of 60 °C, reaction time 24 h, 30% water content and 4% enzyme addition) with RMIM as catalyst, and camellia seed oil diacylglycerol (C-DAG) with a content of 62.49% was also given under optimal esterification conditions (vacuum system, 3% enzyme addition, 2% water addition, reaction temperature of 50 oC, and substrate molar ratio of free fatty acid to glycerol of 1:1). The high content of DAG was obtained by a coupled method, which eliminated the purification steps and reduced production costs. C-oil, and C-DAG have been characterized by means of GC, TG, DSC, and GC-IMS. Our results showed that the enzymatic coupling method did not affect the structural composition of the substances themselves, but did affect the crystallization and melting properties of the oils. Moreover, the taste of C-DAG was more delicate flavor than that of C-oil. Finally, the reaction mechanism has been analyzed by means of infrared spectroscopy, which showed that C-oil was mostly hydrolyzed to free fatty acids. C-DAG exhibited ester C-O stretching vibrations in the range 1280–1030 cm-1, indicating successful esterification reaction between camellia seed oil free fatty acids (C-FFAs) and glycerol under catalysis by the enzyme.