Abstract: One-factor-at-a-time and orthogonal array design methods were employed to optimize transesterification conditions for lipase catalyzed synthesis of scorbyl fatty acid esters from lard and ascorbic acid with ultrasound assistance. The optimum synthesis conditions of scorbyl fatty acid esters were tert-amyl alcohol as reaction medium, Novozym 435 lipase amount of 20% (calculated on the basis of the mass of ascorbic acid), molar ratio of ascorbic acid to lard of 1:3, ultrasound power of 350 W, ultrasound frequency of 59 kHz and reaction time of 9 h, and the resulting conversion rate of ascorbyl fatty acid esters was up to 88.00%. The ultrasonic treatment could improve scorbyl fatty acid ester yield from 71% to 88% and reduce the reaction time from 32 to 9 h. Novozym 435 exhibited excellent stability under the ultrasonic treatment condition and its activity remained at a relatively high level even after its sixth repeated use.

Key words: lard, lipase, ascorbyl fatty acid ester, ultrasonic treatment, transesterification