Revealing wet pulverizing characteristics of cereals and legumes

Abstract

This study aimed to reveal the effects of inherent properties of cereals and legumes on the wet fragmentation process, pulverizing degree, and particle size distribution. The results demonstrated that both mechanical forces and water dissolution had effect on the wet fragmentation process. Grains were first pulverized into smaller granules by mechanical forces, exposing the cut intracellular components. The intracellular matrix was then dissolved in water to separate the embedded starch, leaving the empty cell wall skeleton that was subsequently pulverized into fragments. Legumes had the higher soluble component content and were thus subject to greater water dissolution than cereals. The degree of pulverizing was negatively correlated with thousand grains weight, yield force, and breakage force of raw materials. In situ nano-mechanical experiment showed that the modulus of fiber and adhesion of protein were greater than those of starch, thus the grains with high fiber and protein content but low starch content were more difficult to pulverize. The particle size distribution curves of all pulverized samples were bimodal. The particle size and height of left peak were positively correlated with the size of single starch granule and starch content, respectively. The height of right peak was positively correlated with fiber content. In conclusion, the mechanical and compositional properties of cereals and legumes affected the wet pulverizing characteristics. These findings provide insights for the efficient pulverizing of cereals and legumes and the improvement of product quality.