The effects of moisture content and loading orientation on some physical and mechanical properties of tiger nut

The physical and mechanical properties of the newly “Zhongyousha No.1” and the traditional “Yousha” Chinese tiger nut varieties are studied. Several physical and mechanical properties of the two tiger nut varieties were determined as a function of moisture content (at five levels of 40.0, 32.0, 24.0, 16.0 and 8.0% wet basis). The physical and mechanical properties including length, width, thickness, geometric mean diameter, surface area, sphericity, compression rupture force, firmness, shear rupture force and shear strength. All tiger nut mechanical properties were significantly affected by moisture content (P<0.01). The results shows that the physical properties decreased linearly by decreasing moisture content. The compression rupture force increased linearly from the average of 175.56-208.77 N as moisture content increased from 8 to 40%. While for the shear rupture force and shear strength decreased linearly from the average of 109.73-91.72 N and 1.03-0.63 MPa, respectively. There is a quadratic relationship between firmness and moisture content from the average of 51.80-65.20 N/m. The compression rupture force in the vertical loading orientation is significantly greater than that of the horizontal, while the shear rupture force is higher in the vertical than horizontal. “Yousha” tiger nut possessed higher mechanical strength than “Zhongyousha No.1”. The results can be used as design parameters for suitable harvesting machinery and food processing equipment. © 2021 Long Wang, Can Hu, Wensong Guo, Xiaowei He, Xufeng Wang, Jianming Jian and Shulin Hou.