MECHANICAL PROPERTIES AND MICROSTRUCTURE ANALYSIS OF TPA IN APPLE PULP BASED ON DIFFERENT LOADING SPEEDS

In order to enrich the apple quality evaluation system, TPA mechanical tests were carried out on Fuji, Guoguang and Golden delicious apple pulp at 10 loading speeds of 0.01, 0.1, 0.5, 1, 2, 5, 9, 13 and 17 mm/s, and the mechanical characteristic parameters of pulp were obtained. The effects of loading speed on pulp hardness, elasticity, cohesiveness, chewiness and resilience were analysed. The microstructure of pulp of different varieties pulp was observed by laser confocal microscope. Based on the Voronoi model of pulp tissue structure, the compression test was simulated to construct the relationship between microstructure and mechanical properties. The results showed that the loading speeds had a certain effect on the cohesiveness and chewiness, and had a linear relationship with the cohesiveness of Guoguang variety and the chewiness of Golden delicious. The microstructure of pulp directly determines its mechanical properties, the smaller the roundness of cells and pores, the greater the hardness, cohesiveness, chewiness and resilience. Using Abaqus for compression test simulation, the maximum deviation of stress is 4.3%, which proves that the model is effective and the accuracy is improved. The results provide technical parameters for mechanical system improvements for apple during harvesting, storing and transporting and perfect evaluation system of apple texture.