Effect of hardness on the mechanical properties of kiwifruit peel and flesh

Abstract

ABSTRACT The mechanical properties of kiwifruit serve as the foundation for mechanical damage. In this work, the effect of hardness on the mechanical properties of kiwifruit was explored, and a hardness-mechanical property prediction model was developed. The results in this study showed that the tensile strength of the kiwifruit peel increased with decreasing hardness by 0.51, 0.75, 0.83, and 1.02 MPa in the axial direction and 0.48, 0.68, 0.92, and 1.08 MPa in the radial direction, respectively. While the peel’s elastic modulus decreased by 21.15, 14.03, 11.87, and 10.52 MPa in the axial direction and 15.04, 10.68, 8.45, and 7.54 MPa in the radial direction. At the same ripening stage, peel tensile strength did not differ significantly (P > .05), whereas peel modulus of elasticity was greater in the axial direction than in the radial direction. The results of the flesh compression test showed that the compressive strength of the flesh decreased with decreasing hardness to 0.36, 0.25, 0.09, and 0.06 MPa in the axial direction and 0.36, 0.23, 0.11, and 0.06 MPa in the radial direction, respectively. The modulus of elasticity also decreased to 1.05, 0.82, 0.42, and 0.32 MPa in the axial direction and 0.26, 0.45, 0.80, and 1.15 MPa in the radial direction, respectively. The compressive strength and modulus of elasticity of kiwifruit flesh did not differ significantly in the axial and radial directions at the same stage of ripening (P > .05). The model’s accuracy is demonstrated by correlation coefficients of tensile strength (compressive strength) and elastic modulus of kiwifruit peel and pulp in axial and radial directions, which were 0.97, 0.99 (0.99, 0.99), and 0.93, 0.90 (0.96, 0.99), respectively, for anticipating the mechanical characteristics of peel and flesh. It can provide theoretical and data references for post-harvest kiwifruit to reduce the mechanical damage.