Microwave drying and grinding characteristics of wheat ( Triticum aestivum)

Abstract

Wheat samples of approximately 20 g each were dried in a domestic microwave oven for different time periods ranging from 15 to 150 s with different moisture contents ranging from 0.11 to 0.23 kg of water/kg of dry weight of solids. The samples showed an average moisture loss of 4.4–10.6×10 −4 kg of water/kg of dry weight of solids per second. The dried samples were ground in a domestic dry grinder, and the ground samples were subjected to sieve analysis to calculate the average final particle size. The grinding characteristics were evaluated by calculating the Bond’s work index. The microwave dried samples for 120 s were crisp and consumed less energy for grinding compared to the control samples. The same trend was maintained even when the wheat samples were dried in bulk by taking 1 kg of sample (initial moisture content of 0.11 dry weight basis) and dried for 15 min. The Bond’s work index for the bulk sample was 2.26 compared to 2.41 kW h kg −1 for the control of the equal moisture content. Studies were also made on the effect of the microwave power supply on drying and grinding, and this was found to have effect on the latter. These studies have all indicated that microwave drying of wheat samples before grinding helps reduce power consumption in due course in wheat milling industries. The microwave drying did not change the total protein content, but there were some functional changes in the protein which was evident from the gluten measurements.