## 5 Conclusions  
In this study, we selected three representative cucumbers with distinct flavors (better-tasting cucumber YX, Northern China-type cucumber KX, and pickled-type cucumber GX) from 30 cucumber cultivars based on flavor-quality evaluation. The volatile compounds of fresh fruits of these three cultivars were determined by automatic headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry. A total of 163 VOCs were detected in 18 cucumber flesh samples, which consisted of 13 kinds of compounds, including amines, alcohols, aromatics, phenols, sulfur compounds, halogenated hydrocarbons, aldehydes, acids, terpenoids, hydrocarbons, ketones, heterocyclic compounds, and esters, where the contents of YX were higher than those of KX and GX. In our research, heterocyclic compounds, hydrocarbons, and aldehydes were the most abundant detected compounds in cluster analysis. Through difference analysis, a total of 43 differential metabolites were selected, of which 38 were detected, and the content of YX was higher than that of GX and KX. Only three differential metabolites were identified in all three groups, and the contents were still the highest in YX, namely, alpha-cadinol, \(N\)-(2,3,4-trifluorobenzoyl)-l-alanine-methyl ester, and [3S-(3-alpha,5-alpha,8-alpha.)]-5-azulenemethanol,1,2,3,4,5,6,7,8-octahydro-alpha,alpha,3,8-tetramethyl-acetate. These three compounds have not been reported before. The results of this study are helpful in guiding the identification of VOCs and quality modification of cucumber cultivars.  
The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/foods11081101/s1](https://www.mdpi.com/article/10.3390/foods11081101/s1)]([https://www.mdpi.com/article/10.3390/foods11081101/s1](https://www.mdpi.com/article/10.3390/foods11081101/s1)), Table S1: Information on VOCs contained in all samples; Table S2: Information on differential metabolites of YX vs. GX; Table S3: Information on differential metabolites of YX vs. KX; Table S4: Information on differential metabolites of KX vs. GX.  
Conceptualization, J.Z. and X.C.; methodology, [PERSON] and X.G.; software, X.X.; validation, J.Z. and X.G.; formal analysis, X.G. and X.X.; investigation, W.Y.; resources, X.X and X.C.; data curation, J.Z. and L.L.; writing--original draft preparation, J.Z.; writing--review and editing, X.X. and X.C.; visualization, X.X.; project administration, X.C. and X.X.; funding acquisition, X.C. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Jiangsu Agricultural Innovation of New Cultivars (PZCZ201720); the Jiangsu Agriculture Science and Technology Innovation Fund (CX(20)3165); the Open Project Program of Jiangsu Key Laboratory for Horticultural Crop Genetic Improvement (K2020030) and the Open Project Program of Joint International Research Laboratory of Agriculture and Agri-Product Safety, the Ministry of Education of China (JILAR-KF202001).  
Not applicable.  
Data Availability Statement: Data a contained within the article or Supplementary Material.  
We thank the anonymous reviewers for invaluable comments on this manuscript.  
The authors declare no conflict of interest.