Synthesis of polyglycerol fatty acid esters catalyzed by lipase and evaluation of its emulsification properties

The present study investigated the physicochemical properties of the newly synthesized polyglycerol fatty acid esters (PGFEs) and their potential application as food emulsifiers. It turned out that the complete removal of glycerol from crude polyglycerol was achieved by optimizing the molecular distillation temperature (120 °C). Moreover, novozym 435 was used to catalyze the synthesis of PGFEs with different aliphatic chain lengths, and the esterification rate of the obtained products was 93%∼98%. The characteristic absorption peak of the ester carbonyl group was displayed at 1738 cm−1, and that of C–O–C on the ether bond was at 1100 cm−1 and 1048 cm−1. Therefore, the synthesis can be determined to be PGFEs. Their hydrophilic lipophilic balance (HLB) values are >7, which can be used as oil-in-water emulsifiers. When curcumin nanoemulsions were constructed by PGFEs with various aliphatic chains as emulsifiers, it was found that all PGFEs in C10∼C18 can form stable curcumin nanoemulsions (encapsulation rate was >95%). PGFEs with longer aliphatic chains can stabilize nanoemulsions more efficiently (larger droplet sizes and lower ζ-electric potential), and showed better storage and UV stability. Whereas, medium-chain PGFEs emulsions, especially PGC, showed the best curcumin release efficiency, which theoretically supported the application of PGFEs to functional emulsion products.