Authors

Abstract

In order to research the relationship between macroscopic tearing properties and microstructure of peels, Fuji and Danxia peels were performed longitudinal and transverse tearing tests at the shadow side and sunlit side using electronic universal testing machine and the load-displacement curve, tearing force and tearing strength were gained. The peel cross-section microstructure and tearing fracture morphology of peel samples were observed by means of scanning electron microscopy. The results showed that the peel tearing curves were curves with many peaks and the fracture pattern of the tearing peel was the stripping between cells and a certain peak in the tearing curve was formed when the cells were stripped. The apple peel has composite film properties. Tearing strength has differences with different parts of the same peel and the same part of different peel. It is showed that crack shape and pattern of fruit cracking and fruit surface rupture had the character of variety. Tearing strength of Danxia peel was the biggest in two kinds of peels; the significant difference in tearing strength between shadow sides of Danxia peel and Fuji peels existed (p<0.05) and the tearing strength of Danxia longitudinal peel had significant differences (p<0.05) from Fuji longitudinal peel. This reflected that the flexibility of Danxia peel surface was greater and Fuji peel surface was easy to surface rupture injury in the process of fruit growth. Because the Fuji peel cuticle is more uniform and thicker, solid contact is strengthened and the slippage is lessened between epidermal cells; meanwhile, the number of concurrent loaded cells decreased. That results in minor tearing strength of Fuji peel and the apple surface rupture is closely related to cuticle structure of peel through the analysis of peel microstructure. The study provides quantitative evidence of evaluating peel ability of cracking fruit and fruit surface rupture and riches evaluation index of apple peel texture.

Abstract in Chinese

为探索微观组织与苹果果皮抵抗裂果及果面碎裂能力的关系，在微机控制的电子万能试验机上对红富士和丹霞向阳面和向阴面果皮的纵横向进行了撕裂试验，获得果皮撕裂载荷—位移曲线、撕裂力、撕裂强度；采用扫描电子显微镜观察果皮横截面及试样撕裂裂缝形态的显微结构。结果表明：果皮撕裂的载荷—位移曲线为多峰曲线，试样撕裂的破坏模式是以细胞间剥离为主，苹果果皮材料具有复合薄膜的属性；同种果皮不同部位的撕裂强度均不相同，反映出果实裂果及果面碎裂的开裂形状及方式具有多样性；不同品种果皮相同部位的撕裂强度均以丹霞的为最大，2种果皮间的撕裂强度存在显著性差异（ ），丹霞果皮的柔性较好，红富士果皮表面易于开裂；果实裂果及果皮碎裂的发生与果皮上角质层的结构密切相关，角质层均匀致密且较厚时，果实易于开裂。研究结果为苹果果皮抵抗裂果及果面碎裂能力的评价提供力学特性方面的参考依据，丰富苹果果皮质地的评价指标。