Microwave drying and grinding characteristics of gum karaya (Sterculia urens)
1997
Walde, S.G. | Balaswamy, K. | Shivaswamy, R. | Chakkaravarthi, A. | Rao, D.G.
Samples of gum karaya (Sterculia urens) of approximately 35 g each were dried in a domestic microwave oven for different time periods ranging from 10 to 90 s. The samples showed an average moisture loss of 7.5 x 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 were crisp and consumed less energy for grinding compared to the control samples. This was evident from the bulk drying of gum samples of 1.5 kg (initial moisture content 16%) for 20 min. The Bond's work index for this sample was 0.4786 compared to 0.7567 kWh 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 no effect on the latter. These studies have all indicated that microwave drying is a good candidate for drying of gum samples. The rheological studies were carried out with 1% suspensions. They indicate non-Newtonian pseudoplastic flow behaviour and the data fit well to the power law fluid model. The effect of drying time on the flow behaviour index was assessed.
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