Effect of cell wall polysaccharides on the peelability in table grape berries

Boxiang Zhao¹Junfei Bi²Haonan Wang²Mingyuan Wang^3*Wei Ji^2*

• ¹College of Chemical Engineering, Huaqiao University, Xiamen, Fujian Province, China
• ²College of Horticulture, Shanxi Agricultural University, Taigu, Shanxi Province, China
• ³Institute of Horticulture Science and Engineering, College of Chemical Engineering, Huaqiao University, Xiamen, Fujian Province, China

Grape peelability varieties meet the demand for convenience and hygiene and are popular Grape varieties with easy peelability meet consumer demands for convenience and hygiene, making them increasingly popular. Differences in grape peelability are likely associated with variations in cell wall polysaccharide composition in the pulp and skin. Twelve table grape varieties ('Zaoheibao', 'Qiuhongbao', 'Summer Black', 'Black Balado', 'Jinghongbao', 'Lihongbao', 'Flame Seedless', 'Crimson Seedless', 'Wanheibao', 'Wuhecuibao', 'Thompson Seedless' and 'Hutai No.8') were selected to investigate skin-pulp adherence, skin cell morphology, and cell wall polysaccharide content during fruit development. The role of cell wall polysaccharides in peelability was evaluated by assessing skin-pulp adherencce, skin cell morphology, cell wall polysaccharide content, and activities of related degrading enzymes across developmental stages of different grape varieties. Results showed that skin-pulp adherencce decreased during fruit development, with significant varietal differences. 'Black Balado' exhibited the highest adhesion, while 'Flame Seedless' had the lowest. Cluster analysis grouped ten Eurasian grape varieties into two categories. The first group, which was easier to skin, included 'Flame Seedless', 'Thompson Seedless', 'Wuhecuibao', 'Zaoheibao', 'Wanheibao', 'Jinghongbao', 'Lihongbao', 'Qiuhongbao' and 'Wuhebai'.The second group, characterized by poor peelability, included 'Black Balado'. Anatomical observations indicated that looser skin cell layers may facilitate the separation of grape skin from pulp. As fruit developed, cell wall polysaccharide content (cell wall material, cellulose, hemicellulose, protopectin, chelator-soluble pectin, water soluble pectin) decreased, while the activities of related degrading enzymes (cellulase, β-glucosidase, xylanase, xyloglucan endotransglycosylase, β-mannanase, polygalacturonase, pectate lyase, pectin methyl esterase, β-galactosidase, α-L-arabinofuranosidase) gradually increased. Pearson correlation analysis revealed a positive correlation between skin-pulp adherencce and cell wall polysaccharide content in skin and pulp, and a negative correlation with degradation-related enzyme activity. Partial least squares regression analysis revealed that, among cell wall polysaccharides, adherencce was most strongly influenced by cell wall material and cellulose content of the grape pulp cell wall. Among the degradation-related enzymes, cellulase, β-glucosidase, xylanase, xyloglucan endotransglycosylase, and β-mannanase had a greater impact. Principal component analysis confirmed that cell wall material, cellulose content, β-glucosidase, and xylanase are key factors influencing skin-pulp adherencce. This study provides a theoretical framework for understanding the physiological mechanisms underlying grape peelability.