JOURNAL OF FOOD SCIENCE AND TECHNOLOGY-MYSORE, vol.59, no.4, pp.1558-1569, 2022 (SCI-Expanded)
Three distinct drying methods, microwave drying (MWD), convective drying (CVD) and microwave-convective drying (MWCVD) with a grinding process were applied to obtain pumpkin powder. The effects of CVD (60, 70 & 80 degrees C), MWD (100 & 200 W) and MWCVD (100 W-60 degrees C, 100 W-70 degrees C, 100 W-80 degrees C, 200 W-60 degrees C, 200 W-70 degrees C, and 200 W-80 degrees C) applications on the physicochemical properties (water activity, bulk, tapped & particle densities, porosity, flowability, cohesiveness, swelling capacity, water holding capacity and water solubility index), color values (L*, a*, b*, C, alpha(o) and Delta e), bioactive compounds (5-Hydroxymethyl-2-furfural (HMF), total phenolic content (TPC) and antioxidant capacity (DPPH and ABTS)) of the eleven pumpkin fruit powders were compared. The MWCVD, namely pumpkin powders dried at 200 W-80 degrees C resulted in shorter drying times with high-quality dried pumpkin powders. The bulk, tapped and particle densities of pumpkin powders at 200 W-80 degrees C by MWCVD were 0.56, 0.66 and 1.74 g/cm(3), respectively. These values are indicators of the good porosity (61.82%) of pumpkin powders. In addition, the highest TPC (1277.08 mg GA/100 g dw) and ABTS (126.99 +/- 3.31 mu mol Trolox/g dw) was observed for microwave-convective dried pumpkin powders at 200 W-80 degrees C. On the other hand, the lowest HMF level (10.12 +/- 1.78 mg/kg dw) was found for the pumpkin poowders dried by MWCVD at 200 W-80 degrees C. In overall, dried pumpkin powders by a MWCVD method can be employed to acquire a high-quality food material along with an enhanced physicochemical properties, color and bioactive components.