Enzymatic synthesis of lard-based ascorbyl esters in a packed-bed reactor: Optimization by response surface methodology and evaluation of antioxidant properties

An optimal continuous production of lard-based ascorbyl esters (LBAEs) by transesterification of lard with l-ascorbic acid in a packed bed reactor (PBR) was developed using immobilized lipase (Novozym 435) as a catalyst in a tert-amyl alcohol solvent system. Response surface methodology (RSM) and central composite design (CCD) were employed to evaluate the effects of substrate flow rate, reaction temperature and substrate molar concentration ratio on the molar conversion of LBAEs. The optimum conditions were as follows: substrate flow rate 1.07 ml/min, reaction temperature 56.44 °C, and substrate molar concentration ratio 2.24:1. The optimum predicted LBAEs yield was 50.83% and the actual value was 50.50%. The above results shows that the RSM study based on CCD is adaptable for LBAEs yield studied for the current transesterification system. The antioxidant activities of LBAEs has also been studied. LBAEs represented positive antioxidant potential on superoxide anion radical and hydroxyl radicals and satisfactory antioxidant activity in lard and soybean oil. The results suggest that LBAEs has the potential to serve as natural antioxidant in food system.