# Volatile Flavor Profile and Sensory Properties of Vegetable Soybean
## 2 Results and Discussion
### Volatile Compounds  
Volatile compounds are associated with aroma and make important contributions to flavor diversity. In this study, the analysis of volatile substances in the three vegetable soybeans was performed using HS-SPME-GC-MS. The total ion chromatograms of the three vegetable soybeans are shown in Figure 4. Differences among the chromatograms were evident, indicating that the volatile composition of the vegetable soybean varieties had large variability. A total of 41 volatile compounds (Table 3) were identified, versus the 27 components detected by [PERSON] et al. in Japanese vegetable soybean _'Chakaiori'_[22]. They used an acid-phase solvent to extract the aroma compounds and analyzed them through capillary GC-MS. The most abundant flavor compounds that they detected were n-hexanal (0.91%), 1-hexanol (1.79%), 2-hexanal (0.48%), 3-hexene-1-ol (0.49%), and phenylethyl alcohol (0.40%). The 41 volatile compounds were classified into 5 groups according to chemical properties: aldehydes (19), alcohols (5), ketones (5), esters (4), and others (8) (Figure 5a). Aldehydes and alcohols were the main volatile substances. A total of 35 kinds of volatile components were detected in TW292, comprising 2 alcohols, 17 aldehydes, 5 ketones, 3 esters, and 8 others. Among them, nonanal, hexanal, and 1-octen-3-ol had a high content (6.97%, 15.01%, and 41.14%, respectively). In X3, 31 volatile components were identified (2 alcohols, 16 aldehydes, 4 ketones, 4 esters, and 5 others). In X3, 2-octenal, (\(Z\))-2-decenal, hexanal, (\(Z\))-2-heptenal, nonanal, and 1-octen-3-ol were identified as the high-content volatile compounds, which accounted for 6.32%, 7.95%, 8.78%, 9.94%, 10.29%, and 27.80%, respectively. In SX6, 34 volatile components were detected, comprising 5 alcohols, 18 aldehydes, 4 ketones, 2 esters, and 5 others. Nonanal, hexanal, (\(Z\))-2-decenal, (\(Z\))-2-heptenal, and 1-octen-3-ol had high relative content (6.88%, 7.41%, 8.84%, 9.67%, 11.70%, and 18.45%, respectively). For the analysis of the aroma characteristics of vegetable soybeans, a heat map based on peak areas was generated for visualization of difference in main aroma compound composition. As shown in Figure 5b, the evident difference in color showed that the volatile composition of the varieties considerably varied in type and relative content. The  
Figure 3: Radar map of the response of electronic tongues of three vegetable soybeans. Aldehydes are the crucial compounds detected. They are important flavor and fragrance volatiles in many fruits [23]. Hexanal was abundant in the three vegetable soybeans. It contributes a green and grassy off-flavor, which is regarded to be principally responsible for the beauty flavor [24]. (Z)-2-Heptenal, 2-octene, and (Z)-2-decenal were the predominant aldehydes and provided fruity or fat odor notes [25]. Nonanal is naturally found in essential oils, such as rose, citrus, white lemon, and brussels oil, and as a strong oil atmosphere. When diluted, it emits rose and citrus-like aromas. In TW292, hexanal and nonanal had considerably higher relative content than the other aldehydes. Therefore, hexanal and nonanal were identified as the main aldehyde volatile components in TW292. In X3 and SX6, hexanal, (Z)-2-heptenal, 2-octene, nonanal, and (Z)-2-decenal were the main aldehyde volatiles. Alcohols constituted the second largest class of identified volatile compounds in the three vegetable soybeans, especially in TW292. Alcohol provides a pleasant aroma (sweet, floral, or fruity) [26]. The most abundant volatile substance detected was 1-octen-3-ol. Its content has a significant impact on the flavor of vegetable soybeans because 1-octen-3-ol has a pleasant loamy aroma and a strong herbal fragrance, similar to the aroma of lavender, rose, and hay. This study showed that 1-octen-3-ol was the main volatile component in vegetable soybeans.