This study aimed to establish a scientific framework for cucumber fruit quality evaluation by integrating the analysis of nutritional traits and flavor compound profiles across diverse germplasm resources with human sensory evaluation.

Twelve cucumber lines/varieties with significant sensory variation (provided by Tianjin Cucumber Research Institute) were investigated. The measurements included three parts: first, nutritional traits of fruits, such as soluble sugar content (SSC), total soluble solids (TSS), and titratable acidity (TA); second, flavor compound content in fruits, such as total volatiles and key aldehydes [(E, Z)-2, 6-nonadienal, (E)-2-nonenal, (Z)-6-nonenal]; third, sensory evaluation of fruit quality, such as sweetness, juiciness, crispness, aroma, non-astringency, and non-bitterness. An integrated correlation analysis was performed to link sensory attributes with physicochemical profiles.

In the sensory evaluation, non-astringency and sweetness had the highest weighting coefficients (27.12% and 25.49%, respectively), while the other four attributes (aroma, crispness, non-bitterness, and juiciness) ranged from 10.59% to 12.51%. Higher scores across these six dimensions indicated superior overall sensory quality. Furthermore, sweetness, juiciness, crispness, aroma, and non-bitterness of cucumber fruit sensory evaluation were (extremely) correlated with the SSC, TSS content and ascorbic acid content. In addition, cucumber flavor compounds (Z)-6-nonenal content showed significant correlation with sweetness, aroma, juiciness, non-bitterness and non-astringency in sensory evaluation, and it also had extremely significant positive correlation with the SSC, TSS and ascorbic acid content, respectively, while the ratio of cucumber flavor compounds (E, Z)-2, 6-nonadienal to (E)-2-nonenal was significantly correlated with non-astringency. Among the different cucumber varieties tested, line L2 generally exhibited higher levels of fruit SSC, TSS and ascorbic acid content, as well as the ratio of soluble solid content to titratable acid compared with the other lines. It also achieved the highest composite score across all those six sensory attributes. Consequently, line L2 demonstrated superior overall fruit quality.

The SSC, TSS, ascorbic acid content, (Z)-6-nonenal content, and the ratio of (E, Z)-2, 6-nonadienal to (E)-2-nonenal content of cucumber fruits could serve as effective indicators for the rapid evaluation of sensory and flavor quality.