Authors

Abstract

Fruit and vegetable peels exert a protective effect on fruits as constituent parts of the outermost tissue and their properties are of great importance to reducing fruit and vegetable mechanical injury. Four kinds of fruit and vegetable peels such as Nagafu apple, Crisp pear, Tainong mango and long eggplant were chosen to perform longitudinal and transverse tests of tensile property by means of electronic universal testing machine. Stress-strain curve, tensile strength, elastic modulus and fracture strain of peels were obtained; and the microstructures of four kinds of peels were scanned using an electron microscope (SEM). The results indicated that cubic polynomials proved superior for quantifying the stress-strain non-linear relationship of peels and the fitting error of tensile strength is less than 10 parts per thousand. Tensile strength, elastic modulus and fracture strain of peels were different in the case of different fruits and vegetables cultivated and different parts of the same peel; fruit and vegetable peels belong to anisotropic heterogeneous materials and have certain strength. The mean values of tensile strength and fracture strain of the long eggplant peel are the biggest in four kinds of peels and that of elastic modulus of Nagafu apple peel is the largest; long eggplant and Nagafu apple peels had better resistance to damage sensibility than Crisp pear peel. The bearing capacity of the peels depends on the number, width and distribution of microcracks on the surface, and the shape of the epidermal cells and fruit dot on peels; the number of microcracks is bigger and the width of microcracks is wider, the tensile strength is smaller and the elastic modulus of peel is bigger with the slippage increase of epidermis cells. This study provides basic technical parameters for mechanical equipment design for fruit and vegetable during harvesting, processing, packaging, storing and transporting and builds the correlations between macro-mechanics properties and microstructures of fruit and vegetable peels.

Abstract in Chinese

果蔬果皮作为果实最外层的组成部分，对果实起到保护作用，降低果蔬果实的机械损伤。在微机控制的电子万能试验机上对长富苹果、酥梨、台农芒果和长茄子果皮进行了拉伸力学性能试验，获得果皮拉伸应力—应变曲线、抗拉强度、弹性模量、断裂应变；采用扫描电子显微镜观测果皮微观组织结构。试验结果表明：不同果蔬品种及同种果蔬果皮不同部位间，果皮的力学性能均有差异，果蔬果皮属各项异性材料，具有一定的强度；4种果蔬果皮的抗拉强度、断裂应变平均值均以长茄子的为最大，酥梨的为最小，而弹性模量则以长富苹果的为最大，芒果的为最小，反映出长茄子、长富苹果果皮对损伤敏感性低于酥梨果皮；果皮承载能力取决于表皮上微裂纹的数量、宽度及分布状态、表皮细胞及果点的形状等。研究结果为苹果、酥梨、台农芒果和长茄子果皮力学模型的建立及4种果蔬采收、加工、包装等机械装备的设计提供力学参数，构建果皮宏观力学性质与微观组织结构的联系。