Study on Differences in Firmness Changes of Peach Based on Quantitative Analysis of Cell Micromorphological

In order to quantitatively analysis the changes in cell micromorphology and firmness of peach fruits with different texture, the texture analyzer, multiple microscopic imaging techniques and computer processing technology were used to measure the firmness and cell morphology parameters of pulp and peel of peach fruits (“Meirui”, “Shenzhou Shuimi”, and “Gold baby 5”) during storage. The results showed that both peel-firmness and pulp-firmness were significantly decreased along with the storage. Especially, pulp-firmness showed the more significant reduction (58.68%-78.20%) than the peel-firmness (35.53%-65.19%), making it more suitable for the characterization of peach fruit softening. At the initial storage (1 d), the cell morphology of peach pulp was regular and closely arranged. Specially, the largest cell cross-sectional area (A) (1 500-33 000 μm²) was obtained in “Shenzhou Shuimi”. The cell roundness of 0.70-0.90 were accounted for 92.80% in “Gold baby 5”. With the prolong of storage, the serious fusion in cell morphology was shown in “Shenzhou Shuimi” along with the large cells (A>35 000 μm²) appeared. For “Meirui”, the cell cross-sectional porosity was continuously increased during the storage, attributing to the cell shrinkage. “Gold baby 5” showed the lowest increase ratio in cell cross-sectional circumference, as well as the smallest amplitudes of cell deformation. Results of scanning electron microscope and transmission electron microscope were confirmed that during the storage, melting peach “Shenzhou Shuimi” with the loosest structure showed the severe degradation of cell wall and the most obvious dissolution of cytoplasm, while the non-melting peach “Gold baby 5” showed the relatively complete cell structure and small dissolution of cytoplasm. For stony hard peach “Meirui”, the round cell transferred to the oval cell and the change degree in structure was between melting and non-melting peaches. Therefore, based on the quantitative analysis of cell micromorphology, the differential changes in firmness of peach fruit with different texture were clarified, aiming to provide the theoretical basis for grading and quantitatively characterizing the changes of cell morphology and firmness of peach fruit based on texture difference.