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.