Abstract

Exposure of Escherichia coli to microwave treatments results in a reduction of the microbial population in apple juice. This research determined the effect of pasteurisation at different power levels (270-900 W) on the microbial quality of apple juice, using a home 2450 MHz microwave. Data obtained were compared with conventional pasteurisation (83°C for 30 s). Apple juice pasteurisation at 720-900 W for 60-90 s resulted in a 2-4 logs population reduction. Using a linear model, the D-values ranged from 0.42±0.03 min at 900 W to 3.88±0.26 min at 270 W. The value for z was 652.5±2.16 W (58.5±0.4 °C). These observations indicate that inactivation of E. coli is due to heat.