Optimal production and structural characterization of erythorbyl laurate obtained through lipase-catalyzed esterification

Erythorbic acid, a stereoisomer of L-ascorbic acid, has been extensively used as an antioxidant but cannot be applied to lipid-based foods due to its poor lipophilicity. For this reason, synthesis of erythorbyl laurate (6-O-lauroyl-erythorbate) was achieved in acetonitrile using an immobilized lipase from Candida antarctica as a biocatalyst to increase its lipophilicity. Response surface methodology was used to optimize the erythorbyl laurate synthesis conditions in terms of enzyme content (1,000-5,000 propyl laurate unit, PLU), molar ratio of lauric acid to erythorbic acid (5-25), and reaction temperature (25-65°C). The central composite experimental results showed the conditions for maximum molar conversion yield were as follows: enzyme content, 2,994 PLU; lauric acid to erythorbic acid molar ratio, 24. 23; and reaction temperature, 53. 03°C. The maximum molar conversion yield reached 77. 81%, which was in agreement with the predicted value (76. 92%). The erythorbyl laurate was purified and identified by Fourier transform-infrared spectroscopy (FT-IR). This research could help to develop an economical method of synthesizing erythorbyl laurate for use as a novel foodgrade emulsifier with antioxidative activity.