Abstract: Human milk fat substitutes (HMFS) were prepared by a two-step enzymatic procedure. Firstly, triacylglycerols (TAGs) rich in palmitic acid (PA) at Sn-2 position were synthesized by Novozym 435 lipase-catalyzed acidolysis of camellia seed oil with palmitic acid in organic system. The optimal alcoholysis conditions were determined using one-factor-ata- time experiments and response surface methodology as follows: n-hexane as reaction solvent at a dosage of 10 mL/g; palmitic acid/camellia seed oil mass ratio, 1.1:1; lipase dosage (on the basis of substrate mass), 10.1%; reaction time, 16.5 h; and temperature, 50 ℃. Under these conditions, TAGs with 66.08% PA at Sn-2 position were obtained. Then HMFS were synthesized by transesterification of these TAGs with fish oil catalyzed by the Sn-1,3 specific lipase Lipozyme TL IM. The final product was tested, and the results showed that the content and distribution of palmitic acid in the HMFS were similar to those of human milk fat. Besides, it had high levels of eicosapentaenoic acid (EPA), and docosahexenoic acid (DHA). Therefore, the HMFS could be used as a fat source for infant formula.

Key words: human milk fat substitutes, camellia seed oil, lipase, fish oil, polyunsaturated fatty acids