| With the rapid improvement of consumer living standards,the development of green,healthy,nutritious and safe food has become increasingly important.Among these aspects,research and development of food antioxidants plays a crucial role.L-ascorbyl palmitate（LAP）is the only approved antioxidant for use in infant formula that is both safe and effective.However,its current production process relies on chemical synthesis which presents challenges such as equipment corrosion,high energy consumption,and generation of large amounts of acidic wastewater that do not align with sustainable development goals.Moreover,the application and antioxidant effect of LAP are significantly limited by its high melting point and poor solubility in fats.Therefore,it is of great significance to study green and efficient methods for preparing LAP and create a new series of lipid-soluble LAP products.An ordered mesoporous silicone lipase microarray was prepared and utilized as a catalyst for the successful enzymatic synthesis of L-ascorbic acid unsaturated fatty acid esters（UFAAE）in this thesis.Subsequently,the melting properties and antioxidant capacity of UFAAE in various vegetable oils were systematically evaluated.1.The ordered mesoporous silica lipase microarray（Ca LB@OMS-C8）,with a catalytic efficiency（CE）of 20.8 M g-1 h-1,was 2.7 times higher than that of the free lipase,it enhanced the catalytic activity and thermal stability of the free lipase.This demonstrated that the home-made Ca LB@OMS-C8 lipase microarray could effectively replace the free lipase Ca LB and the commercial Novozym 435.2.The optimal process conditions for catalytic synthesis of L-ascorbic acid esters were determined as follows:tert-butanol was used as the reaction solvent,and oleic,linoleic,and linolenic acids were used as raw materials.The concentration of L-ascorbic acid was 0.04M with a molar ratio of 1:5 to fatty acids.Lipase concentration was set at 7.4 g/L while molecular sieve addition was set at 60 g/L.Three distinct L-ascorbic acid esters were successfully synthesized under these conditions at 70°C for a duration of 4 h.3.The conversion rates of different L-ascorbic acid esters,including L-Ascorbyl oleate（LAO）,L-Ascorbyl Linoleate（LAL）,and L-Ascorbyl Linolenic Acid Ester（LALN）,were71.8%,74.1%,and 76.8%,respectively.Molecular docking was employed to simulate and elucidate the disparities in rates of fatty acid esterification,revealing that linolenic acid exhibited the most robust binding affinity with lipase（-18.8 k J/mol）.The application of molecular docking analysis can facilitate the screening of suitable acyl donors,which is pivotal for enhancing enzyme yield and curtailing operational expenses.4.LAP has a solubility of only 0.02 g/100g in rapeseed oil,whereas the solubility of LAO,LAL,and LALN with added oleic acid,linoleic acid,and linolenic acid,respectively,was0.16,0.38,and 0.40 g/100g,which increased the solubility of LAP by 7-20 times.The findings indicate that utilizing unsaturated fatty acids in the synthesis of L-ascorbic acid esters is a viable approach to enhance their lipid solubility.Additionally,the comparable oxidation induction periods of UFAAE and LAP across various oils validate the feasibility of UFAAE as an antioxidant. |
