Diversity of Volatile Profiles and Nutritional Traits Among 29 Cucumber Cultivars

Twenty-nine samples of two cucumber types (Cucumis sativus L.) were evaluated to determine the amino acid, tannin, soluble protein, soluble sugar, Vc, nitrate nitrogen contents and volatile organic compounds (VOCs). Cucumber variety differences in amino acid, tannin, soluble proteins, et al., were significant (p < 0.05). The VOCs were derived by headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). A total of 67 VOCs were identified, including 24 aldehydes, 13 alcohols, 12 ketones, 12 alkenes and 6 other compounds. (E, Z)-2,6-Nonadienal, (E)-2-Nonenal and (E)-6-Nonenal were the three most abundant volatiles. A total of 21 VOCs were present in all 29 cultivars. An average of 45 kinds of VOCs were identified in each cultivar. Principal component analysis (PCA) clustered the 29 cucumber cultivars into five groups. Partial least-squares-discriminant analysis (PLS-DA) indicated that the European type was separated from the South China type across PLS1. Furthermore, 25 key differential volatiles for distinguishing 29 cultivars and 23 key differential volatiles for differentiating between South China and European types were identified, respectively. These results provide information for the development of new cultivars with high nutritional quality and intense flavor.