# Quality Characteristics and Flavor Analysis of Five Mulberry Varieties
## 3 Results and Discussion
### Volatile Components
The total content of alcohol components was the highest in White Shahtoot Mulberry, followed by Yuesang 10, 2000-3, Zhongsang 5801, and Jialing 40 (Figure 5A). Among alcohols, only 6-methyl-2-heptanol and 1-dodecanol have an OAV > 1, but their flavor description is unclear. 6-Methyl-2-heptanol was abundant in White Shahtoot Mulberry, at 19.83 \(\pm\) 8.63 mg/kg (Supplementary Table S1). Aldehydes significantly contribute to the complexity of fruit flavors [66]. In total, 20 aldehydes were identified in the five varieties, including nonanal and (E)-2-nonenal. Hexaldehyde (0-1.58 mg/kg), 2-ocrenal (0-0.11 mg/kg), (E)-2-nonenal (0.51-3.07 mg/kg), 2,4-nonadienal (0-0.12 mg/kg), and other compounds were relatively abundant in the five species of mulberries, which is consistent with previous studies [18]. Aldehydes such as hexaldehyde, nonanal, decanal, (E)-2-hexenal, (E)-2-nonenal, and (E)-2-ocrenal may be closely related to green odors, whereas general aldehydes containing 6-10 carbon atoms are related to both green and fatty aromas [67]. There are 12 aldehydes with an OAV > 1. Hexaldehyde, decanal, (E)-2-decenaldehyde, and 2,4-decadienal substances, unique to White Shahtoot Mulberry, provide it with apple, fat, fresh, orange peel, penetrating, coriander, and other flavors. The unique 2-Octenal, (Z)-4-decenaldehyde, and 2,4-nonadienal of 2000-3 provide dandelion, fat, fruit, grass, green, spice, cereal, and other flavors. Ketones are volatile components, and a high total ketone content was detected in many mulberry varieties. Among the five varieties, Yuesang 10 had the highest ketone content (Figure 5A). Furthermore, ketones can give fruits a special smell, such as 5-hexyldihydro-2(3H)-furanone providing fruits a \"buttery\" and \"sweet\" flavor [18]. 2-Octanone can bring fat, fragrant, and mold flavors to mulberries. The content of volatile acid components in Yuesang 10 was the highest (Figure 5A). Pentadecanoic acid was identified in 2000-3, Jialing 40, Yuesang 10, and White Shahtoot Mulberry. Among these mulberry varieties, Yuesang 10 contained the highest content of pentadecanoic acid, at 7.36 \(\pm\) 2.91 mg/kg (Supplementary Table S1) in the acidic fraction. Figure 5: Contents and types of volatile components in the five mulberry varieties. (**A**) Classification and content of volatile compounds in different mulberry varieties. (**B**) Venn diagram of volatile substances. Despite this, pentadecanoic acid had an OAV < 1. This shows that although its content was relatively high, it had no significant contribution to the flavor of the mulberries. In general, the 66 volatile components identified through GC-MS differed significantly in the distinct mulberry varieties. The high ester and aldehyde concentration distinguished Yuesang 10, whereas White Shahtoot Mulberry had higher alcohol concentrations than the other varieties. In this study, the quantities and contents of volatile components were higher in Yuesang 10 and White Shahtoot Mulberry than in the other three varieties. This suggests that Yuesang 10 and White Shahtoot Mulberry have richer and more intense aromas than the other three varieties. It is reported that fatty acids and amino acids are the precursors in the metabolic pathway of volatile components, and they can be converted into aromatic volatile substances through a series of biochemical reactions in the plant [68; 69]. At present, there are few studies on their transformation pathway in mulberries, and it is still unclear. Future research could further explore the specific relationship between them. This provides some ideas for future research.