Effects of repeated rewetting and drying on breakage and moisture desorption characteristics of soybeans.
Asota, Celestine Ngozi.
Thesis of Ph.D., The University of Wisconsin - Madison, 1987, 307 pages
1987
บทคัดย่อ
The effects of postharvest rewetting/drying cycles on grain breakage and desorption characteristics were investigated in a laboratory study. Grain breakage was quantified with three characteristics (breakage susceptibility, compressive resistance and fracture resistance) which were simultaneously measured during the rewetting and drying treatments. The effects were examined in the drying temperature and time domain using response surface contours constructed from second order approximating functions.
Soybeans exhibited systematic changes in the properties within the 5%-18% moisture range (wet basis) and showed optimum quality when dried at 50circC-80circC for less than 10 hours or below 50circC for more than 100 hours.
Statistical analysis showed that the interaction between rewetting and drying was significant. When rewetted beans were dried with unheated air, they showed greater cotyledonous splits than when dried with heated air but without appreciable change in breakage susceptibility. The effects of the rewetting/drying treatments were statistically similar for fracture resistance and compressive resistance, with significant increase in these properties recorded during the first rewetting treatment only. When rewetted beans were dried with heated air, the treatments were found to increase their drying rates and to decrease the rate of change of breakage susceptibility with drying. Resistance to compression of the beans also decreased with increase in the drying temperature.
Sensitivity analytical procedure was employed to reveal minute deviations in the measured characteristics caused by the treatments. The induced changes in the compressive property were largest at the moisture region corresponding to the peak values in the property. Whereas the induced change in the moisture desorption characteristics increased with increases in the number of rewetting treatments prior to 60 hours of drying, increase in the induced change in breakage susceptibility was not possible within 0%-10% moisture level.
Kinetic information obtained from the isothermal drying of soybeans was used to develop a moisture correction procedure in mechanical testing of soybeans to account for changes in the properties contributed by changes in the test environment.