Comparative Study Of Conventional And Microwave Blanching On Peroxidase Activity And Color Of Ehretia asperula Leaves

Abstract

This study aimed to investigate the effects of blanching methods on peroxidase (POD) activity and color of Ehretia asperula (E. asperula) leaves. E. asperula leaves were blanched for 0-180 s at 70-90 °C using a water bath or at 300-500 W using a microwave oven. The results showed that POD inactivation rate constants increased with temperature/microwave power, whereas the D-value showed an opposite trend. The highest k and lowest D-value were observed in hot water blanching (HWB) at 90 °C (0.0258 s^-1 and 101 s) and microwave blanching (MWB) at 500 W (0.0271 s^-1 and 86 s) (p > 0.05). HWB and MWB also showed similar effects on L*a*b* coordinates, which was characterized with the increase in L* and b*, and the decline in a*. However, HWB at 90 °C (k for a* = 0.1034 s^-1) showed a double quicker changes in a* coordinate compared to MWB at 500 W (k for a* = 0.0506 s^-1) to reach the equillibrium a* value of -4.19. These findings indicate that both HWB and MWB show similar impacts on POD activity and color of E. asperula leaves in most cases. HWB can be more useful in the industrial scale, where requires a larger capacity; while the laboratory preparation of blanched E. asperula leaves can benefit from MWB due to minimal preparation and lower water consumption.