A comparative study on the degradation patterns of cell wall pectic materials unveils novel insights into postharvest textural alteration between rapid- and slow/non-mealy apple cultivars

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• ‘Huaniu’ apples showed much rapid cell separation and mealiness than ‘Orin’ apples. • Early ethylene surge in ‘Huaniu’ within 7 d accelerated the mealiness development. • Galactose loss from pectin reduced cell adhesion in mealy ‘Huaniu’ against ‘Orin’. • Crystalline cellulose increased in mealy Huaniu flesh, owing to pectic matrix loss. • Degradation of CSP and SSP pectin fractions promoted the mealiness in Huaniu flesh. Mealiness, characterized by soft, mouth-drying, grainy, and floury sensation, is a major textural deterioration in stored apples. This study investigated the underlying mechanism by comparing the rapid-mealy ‘Huaniu’ apple, which became fully mealy within 14 days (d) at 25°C, with the slow/non-mealy ‘Orin’ apple, which maintained texture beyond 63 d. Texture property analysis indicated that ‘Huaniu’ apples had more rapid changes in hardness, expressible juice, cohesiveness, and springiness than ‘Orin’ apples. A sharp early surge in ethylene production and respiration intensity occurred in ‘Huaniu’ by 7 d, dramatically earlier than that in ‘Orin’ (49 d). Immunolabelling revealed a decrease in homogalacturonan (HG) during mealiness. Notably, cell walls of ‘Huaniu’ exhibited more intense labelling of non-methyl-esterified HG compared to ‘Orin’. The irregular, separated, shriveled and intact cells were observed in ‘Huaniu’ at the mealy stage, while no obvious changes in ‘Orin’. X-ray diffraction, low field nuclear magnetic resonance, and PCA of FTIR data of cell wall materials (CWM) further distinguished the cultivars. Analysis of CWM and pectic fractions (water-soluble pectin (WSP), chelator-soluble pectin (CSP), and sodium carbonate-soluble pectin (SSP)) showed a substantial loss of galactose in ‘Huaniu’, particularly from CSP and SSP. Pearson correlation indicated this galactose depletion likely promoted degradation of galactan side chains in pectin polymers, weakening intercellular adhesion and accelerating mealiness development. The results provide an approach to understand the underlying mechanism of mouthfeel deterioration of apple fruit.