Abstract: Response surface methodology was used to optimize microwave inactivation of myrosinase in maca. Firstly, the effects of three factors such as microwave intensity, microwave treatment time and material-to-liquid ratio on myrosinase activity and glucosinolate content of maca were investigated by one-factor-at-a-time method. Subsequently, a mathematical model for myrosinase activity in maca was established based on a three-variable, three-level central composite design. Finally, response surface analysis was carried out to optimize the above three factors for minimizing relative myrosinase activity. The results showed that the myrosinase in maca could be inactivated completely after 60 s microwave treatment at a microwave intensity of 14 W/g and a material/liquid ratio of 2:1 (g/mL). The losses of glucosinolates and vitamin C in maca subjected to microwave treatment revealed the decrease by 28% and 21% when compared with conventional hot water blanching. Meanwhile, no significant difference in protein loss between both treatment methods was observed.

Key words: maca, microwave inactivation, myrosinase, blanching, glucosinolates