Quality Attributes and Microstructure of Cell Walls in ‘Suli’ Plum Fruit (Prunus salicina Lindl.) during Softening

The quality attributes and cell wall materials of ‘Suli’ plums stored at 4 °C and 25 °C with 80%–90% relative humidity were investigated. Rapid changes in firmness, soluble solids content (SSC), titratable acidity (TA), and decay rate at 25 °C were evaluated. These changes were suppressed in the plums stored at 4 °C. Modification of cell walls in the ‘Suli’ plums was investigated by Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM). FTIR and AFM indicated that low temperature significantly maintained cell wall integrity, as well as suppressed the conversion of protopectin and degradation of pectin during storage. The results confirmed that the microstructures and composition of the cell wall in ‘Suli’ plums were closely related to firmness, which is considered the main index of fruit softening.