Development of novel high power-short time (HPST) microwave assisted commercial decontamination process for dried...

The commercially available dry turmeric powder at 10.34% d.b. moisture content was decontaminated using microwaves at high power density for short time. To avoid the loss of moisture from turmeric due to high microwave power, the drying kinetics were modelled and considered during optimization of microwave decontamination process. The effect of microwave power density (10, 33.5 and 57 W g^-1), exposure time (10, 20 and 30 s) and thickness of turmeric layer (1, 2 and 3 mm) on total plate, total yeast and mold (YMC) counts, color change (∆E), average final temperature of the product (T_af), water activity (a_w), Page model rate constant (k) and total moisture loss (ML) was studied. The perturbation analysis was carried out for all variables. It was found that to achieve more than one log reduction in yeast and mold count, a substantial reduction in moisture content takes place leading to the reduced output. The microwave power density significantly affected the YMC, T_af and a_w of turmeric powder. But the thickness of sample and microwave exposure time showed effect only on T_af, a_w and ML. The colour of turmeric and Page model rate constant were not significantly changed during the process as anticipated. The numerical optimization was done at 57.00 W g^-1 power density, 1.64 mm thickness of sample layer and 30 s exposure time. It resulted into 1.6 × 10⁷ CFU g^-1 YMC, 82.71 °C T_af, 0.383 a_w and 8.41% (d.b.) final moisture content.