Establishment and application of an evaluation system for table grape quality in cold region

This study established a comprehensive quality evaluation system for table grapes cultivated in plastic greenhouses in cold regions. A total of 36 indicators covering appearance, texture, flavor and bioactive properties were measured in 38 cultivars over two consecutive years. Through integrated variability analysis, correlation analysis and principal component analysis, six core attributes were identified and assigned weight coefficients using the analytic hierarchy process. Among these, sugar-acid ratio contributing most (0.366), followed by total phenolics (0.233). A distinctive feature is that total phenolics was set as a variable based on edible part, using skin content for thin-skin grapes and the sum of skin and pulp content for thick-skin grapes. The resulting model, Y = 0.070 × single berry weight + 0.048 × a* + 0.113 × chewiness + 0.169 × total soluble solids + 0.366 × sugar-acid ratio + 0.233 × TP, enabled objective quality scoring. According to composite scores, the 38 cultivars were classified into four grades. Grade I (0.6–0.75) included 10 cultivars, with ‘Summer Black’ achieving the highest score (0.744). Grade II (0.5–0.6) comprised 11 cultivars, while Grades III (0.4–0.5) and IV (0.1–0.4) included the remaining 17 cultivars. Fifteen cultivars (0.729–0.508) bred in China were ranked in Grade I and II. The model was validated through sensory evaluation of 15 randomly selected cultivars, yielding a correlation coefficient of 0.91 between sensory scores and model-calculated values. This study provides a scientifically grounded framework for cultivar screening, quality improvement and sustainable production of table grapes in cold regions.