Mechanical properties and microstructure of potato peels
Li Junwei | Ma Yunhai | Tong Jin | Ma Zichao | Wang Lidong | Yu Jiangtao
Potato peel, as the outermost tissue of the fruit, playing a role of protection and fresh keeping on the pulp tissue, is crucial for the design of potato harvesting machines. In this study, two types of potato ‘Yangyu 4’ and ‘Helan 14’ were selected to conduct friction, tensile and tear tests on their peel. Longitudinal and transverse tensile tests were conducted on the peels of two potato cultivars using an electronic universal testing machine, and tear tests were carried out on peels as well. The static friction coefficient for different materials, stress-strain curves and tear force-deformation curves of the peels were obtained and the tensile strength, elastic modulus, failure strain tear strength of the peels were measured. The results showed that the maximum value of the static friction coefficient against metallic materials was $$0.616 \pm 0.118$$ and $$0.867 \pm 0.104$$ against rubber materials, respectively. The maximum values of the tensile strength, elastic modulus, fracture strain, tear strength were 1.648 MPa, 0.388 MPa, 4.5%, 0.326 kN·m-1, respectively. Scanning electron microscopy images show that many compact and regular polygonal similar-grain grid structures distributed onty the epidermis surface and microcrack basically did not exist on the peel. The spherical micro-convex structures arranged closely and linearly at the boundary of the grid structure. Hierarchical structure surface with spherical micro-convex structures was one of the reasons for its outstanding friction coefficient. The bearing capacity of the peel depended on the number and distribution of grid structures on the surface, and the size and shape of the epidermal cells.
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