Propriedades físicas dos grãos de feijão mungo (Vigna radiata (l.) r. Wilczek) em diferentes teores de água

Abstract

Mung beans, popularly consumed in the form of sprouts and known as moiyashi beans, are commonly consumed in countries such as China, Japan and the USA, among others. Considering the international demand and its high nutritional value, there is the possibility of exporting this legume and, considering that its consumption is more accepted in the form of sprouts, to guarantee an internationally competitive production, the quality of the grain is fundamental. Among the factors that affect the quality of grains, water content is included, influenced by the post-harvest process, mainly drying. The different drying methods and conditions can modify the physical properties of the grains during the water loss process. Thus, the aim of this study was to evaluate the variation in specific mass, angle of repose, porosity and volumetric contraction of mung bean grains during this process. The grains were harvested and threshed manually, with a water content of approximately 35% b.u.. The drying process was carried out in an experimental dryer with a fixed layer, at a temperature of 38.5 ºC, until reaching a final water content of 0.13 dry basis (b.s), monitored by mass difference. The physical properties were analyzed with three replications for pre-established water contents. Apparent specific mass, porosity, angle of repose and volumetric contraction index were determined. The experimental data of volumetric contraction were submitted to a non-linear regression analysis, by the method proposed by Gauss-Newton The selected model was evaluated and defined through values of the observed parameters, such as mean relative error, estimated mean error, coefficient of determination and behavior of residual distribution (RD). The behavior of the angle of repose and the porosity of the mung bean grains was decreasing and linear during the drying process, opposite behavior to that of the specific mass, which increased with the reduction of the water content. The estimated specific mass values increased from 685.45 kg m-3 to 823.3 kg m-3. The angle of repose reduced by 5.6° during drying. The porosity behavior showed a range from 43.3% to 37.3%, between its initial and final water content. It was possible to conclude, for the volumetric contraction index, that the mathematical models Polynomial of second order, Balla and Modified Woods and Corrêa, were the ones that best fit and can satisfactorily describe the phenomenon of the volumetric contraction of the mass, for meeting all the criteria analyzed in the present work.