Abstract

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°C), MWD (100 & 200W) and MWCVD (100W-60 °C, 100W-70 °C, 100W-80 °C, 200W-60 °C, 200W-70 °C, and 200W-80 °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, α o and Δe), 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 200W-80 °C resulted in shorter drying times with high-quality dried pumpkin powders. The bulk, tapped and particle densities of pumpkin powders at 200W-80 °C by MWCVD were 0.56, 0.66 and 1.74g/cm3, respectively. These values are indicators of the good porosity (61.82%) of pumpkin powders. In addition, the highest TPC (1277.08mg GA/100g dw) and ABTS (126.99 ± 3.31µmol Trolox/g dw) was observed for microwave-convective dried pumpkin powders at 200W-80 °C. On the other hand, the lowest HMF level (10.12 ± 1.78mg/kg dw) was found for the pumpkin poowders dried by MWCVD at 200W-80 °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.

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