Integrating hyperspectral imaging to reveal the relationship between postharvest softening and cell wall...

Pineapple fruit undergoes rapid softening during postharvest storage, leading to substantial quality deterioration. This study investigated the relationship between cell wall polysaccharide remodeling, fruit softening, and hyperspectral responses during pineapple storage. Hyperspectral images (900-1950 nm) were acquired alongside analyses of physicochemical properties, cell wall polysaccharides, FTIR spectra, and cell wall microstructure. Firmness loss was closely associated with pectin de-esterification, conversion of ionic- and chelator-soluble pectin into water-soluble pectin, and degradation of neutral sugar side chains. The confocal microscopy further revealed progressive disassembly of the cell wall network during softening. Characteristic spectral variations at 960, 1570 and 1820 nm reflected degradation of neutral sugar, and cell wall polysaccharide remodeling. The SNV-RF model achieved the best firmness prediction (Rp² = 0.862, RPD = 2.669), while the SPA-SVMR model accurately predicted water-soluble pectin (Rp² = 0.928, RPD = 3.78), further demonstrating the capability of hyperspectral imaging to monitor cell wall polysaccharide remodeling during fruit softening. These findings provide mechanistic insights into the association between hyperspectral responses, cell wall polysaccharide remodeling, and firmness loss, highlighting the potential of hyperspectral imaging as a rapid and non-destructive approach for monitoring postharvest softening progression in pineapple fruit.