DRYING RATES OF 25 ARGENTINEAN VARIETIES OF SOYBEAN - A COMPARATIVE-STUDY

Argentinian soybean production reached almost 11 million tonnes in 1991, after a growth of 660% in 14 years. Soybean drying became a major post-harvest activity involving long drying times and high fuel consumption. Thus, production of varieties with high drying rates should be encouraged. In this work, the drying rates of 25 varieties of soybean were determined at 60-degrees-C in a laboratory dryer. Drying times required to reduce the dimensionless moisture from 1 to 0.5 were 97.3 +/- 11.5 min. An analysis was then performed to explain differences in drying times. Sizes of grains, (radius squared) was a significant cause of the differences in drying time. Effective diffusion coefficients were also determined for the 25 varieties. Values found were 7.62 x 10(-11) m2/s with a variation coefficient of +/- 9.1%. The combination of size and diffusion coefficient accounted for the 93.8% of the variations in drying times. No practical effect of oil and protein content on the drying rate was encountered. The diffusion coefficients tend to be greater for larger grains, probably due to the smaller contribution of the tegument to the grain specific resistance to water movement.