Enzymatic conversion of camellia seed oil into glycerol esters: Synthesis and characterization

The conversion of triacylglycerols 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, single factor optimization experiments were carried out for hydrolysis and esterification respectively. Using Lipozyme® RM IM as catalyst, the maximum percent of C-oil hydrolysis reached 87.14% at the reaction temperature of 60°C, reaction time of 24 h, water content of 30% and enzyme addition amount of 4%. The maximum content of camellia seed oil diacylglycerol (C-DAG) reached 62.49% under the conditions of Lipozyme® RM IM as catalyst, vacuum system, 3% enzyme addition, 2% water addition, reaction temperature of 50°C 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 GC, TG, DSC, and GC-IMS. Our results showed that the enzymatic coupling method did not affect the structural of the substances, but did affect the crystallization and melting properties of the oils. Moreover, the taste of C-DAG was more delicate than C-oil. Finally, the reaction mechanism was analyzed using FTIR spectroscopy, revealing that C-oil was primarily hydrolyzed into 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 catalyzed by lipases.