Experimental study on compression fracture characteristics of wheat grains with different moisture content

Wheat grains are subjected to various external mechanical forces that lead to deformation or even fracture during sowing, harvesting, storage, and processing. Wheat grains with different moisture content exhibit different mechanical properties. Therefore, compressive mechanical properties of wheat grains with different moisture contents at different directions were conducted by TMS-Pro physical properties analyzer in the present paper. Results show that geometric dimensional size of wheat grains increase with moisture content. When compressed at different directions, deformation of wheat grains increase while mechanical properties decrease with moisture content. A crack through endosperm is formed on the back of grains, and finally throughout the whole ventral groove when wheat grains are compressed at the L-axis and H-axis directions. And, cracks form on the contact area between grains and compression plates when grains are compressed at the B-axis direction. Number, length, and width of cracks in wheat grains decrease with moisture content. The gap between starch particles of wheat grains with high moisture content is smaller, combination of internal particles is much tighter, and viscoelasticity is increased. Therefore, mechanical properties of wheat grains should be higher with lesser moisture content during sowing, harvesting, and storage, while it should be lower with bigger moisture content during the processing of grains.