Revealing the dominant role of pectin in softening texture and enhancing drying behaviors of grapes after cold plasma pretreatment.

Cold plasma (CP) pretreatment has emerged as an effective technology to enhance drying efficiency while preserving food quality. This study investigated the influence of CP pretreatment (10-60 s) on the drying characteristics, physicochemical properties, and antioxidant capacity of grapes (Vitis vinifera L.), especially focusing on the modification of pectin polysaccharides. The results demonstrated that CP pretreatment progressively disrupted cell membrane integrity and induced degradation of the cell wall middle lamella, primarily driven by oxidative stress from reactive species. When the treatment duration was extended, significant reductions in hardness and chewiness of grapes were observed, accompanied by increased weight loss and relative electrolyte leakage. Modifications in different pectin fractions revealed that water-soluble pectin (WSP) was more susceptible to structural degradation compared to chelator soluble pectin (CSP) and Na2CO3-soluble pectin (NSP), as evidenced by the depolymerization of homogalacturonan domains and the breakage of neutral sugar side chains. Molecular weight distribution analysis further confirmed extensive depolymerization in WSP, complex structural reorganization in CSP, and relatively stable and entangled structures in NSP. These microstructural changes directly weakened tissue integrity, thereby accelerating the subsequent hot air impingement drying (HAD) process and reducing drying time by 41.81%-68.67%. Notably, grapes treated with CP for 30 s maintained the highest levels of bioactive compounds, including chlorophyll, phenolics, flavonoids, ascorbic acid, as well as strong antioxidant capacity and color attributes. These findings provide mechanistic foundation for optimizing CP processing parameters to balance between drying efficiency and quality preservation in postharvest fruit processing.