Abstract: The purpose of the present study was to explore the application of microwave to inactivate myrosinase in maca. One-factor-at-a-time experiments were carried out to investigate the effects of microwave intensity, treatment time and material-to-liquid ratio on the residual activity of myrosinase and glucosinolate content. Response surface methodology was employed to optimize the operating parameters based on the residual activity of myrosinase. A regression model that describes the residual activity of myrosinase as a function of the operating parameters was established. The results showed that myrosinase in maca almost lost all of its activity under the conditions: microwave intensity 14 W/g, material-to-liquid ratio 2:1, and treatment tine 60 s. In addition to effectively inactivating myrosinase, the microwave treatment resulted in a decrease of 28% and 21% in glucosinolate and VC contents, respectively compared with the traditional hot water blanching time, but had little effect on protein content.

Key words: maca, microwave inactivation, myrosinase, blanching, glucosinolates, response surface methodology (RSM)