## 2 Results and Discussion
### Concentration of Individual Aromas in the Different Families of Volatile Compounds
#### 2.3.2 Alcohols  
A total of six alcohols were identified and quantified in this study (1-propanol, 2-methyl-1-propanol, 3-methyl-1-butanol, 1-hexanol, z-3-hexen-1-ol, and \(\beta\)-phenyl-ethanol) (Tables 3 and 4). These compounds are formed during alcoholic fermentation and some of them are recognized by their strong and pungent smell and taste and they are related with herbaceous notes. As regard individual compounds, 3-methyl-1-butanol, characterized by burnt or malty notes [39], had the highest concentration in all our studied wines for both years, as found in a similar study carried out by [PERSON] et al. [3] in Verdejo La Mancha white wines over five consecutive seasons. Another aroma which has an impact in wines is \(\beta\)-phenylethanol, which is synthesized via the Ehrlich pathway through metabolic reactions that involves transamination of the amino acid, L-phenylalanine, and could contribute to the wine aroma with a note of rose [24]. Nonetheless, 1-propanol and 2-methyl-1-propanol have aromas of alcohol, pungent, solvent, or bitter [40], whereas z-3-hexen-1-ol, which was only detected in 2019, has aromas of cut grass and 1-hexanol has notes of vegetables and grass [35].  
Tables 3 and 4 show that the amounts of alcohols detected in our wines was always higher in 2019 than in 2018, which may be explained by the moment of harvest of the grapes, suggesting that it is possible to obtain wines that are more aromatic [41] with a lower alcoholic degree from grapes that are less mature. [PERSON] et al. [18] established that the reduction of cis-3-hexenol that occurs during grape ripening may be critical to enhancing wine quality, making this compound a significant marker for harvest decisions because of its herbaceous aroma, which enhances green notes in wine. In our study, (z)-3-hexen-1-ol was not detected in 2018 probably due to the degree of maturity of the grapes used. As demonstrated in previous studies [42; 43] the concentration of C6 alcohols decreases as ripening progresses because they are derived from C18 fatty acids via the lipoxygenase pathway and alcohol dehydrogenase, either in situ during grape ripening, or under the oxidative conditions present when fruit is crushed [43; 44].  
More specifically, in 2018, when all the wines elaborated with the white crosses were compared to Verdejo wine, the highest concentration of 1-propanol and 2-methyl-propanol was found in the MV7 wine. By contrast, the concentration of 3 methyl-1-butanol and \(\beta\)-phenyl ethanol were higher in all thewines made from the crosses, and the same applied to 1-hexanol, except in the case of the MC69 wine, in which the concentration was similar to that of Verdejo wine. 3-methyl-1-butanol may contribute to the complexity of the aroma of wines, although values over 400 mg/L can have a negative effect ([PERSON], 2018). In the 2018 season, this compound reached a maximum concentration of 172 mg L\({}^{-1}\) in the MV7 wine. Furthermore, the positive or negative influence of higher alcohols depends on the type of wine and its aroma ([PERSON], 2019). In 2019, Verdejo wine had the highest concentrations of 1-propanol and 3-methyl propanol, and only MC69 wine had a higher concentration of 3-methyl-1-butanol, giving to the wine complexity. By contrast, z-3-hexen-1-ol was detected in all the wines, MC180 and MS82 wines having a higher concentration than Verdejo wine. In the case of 1-hexanol, as in 2018, its concentration was higher in all wines elaborated with the crosses, and \(\beta\)-phenylethanol was only more abundant in MV67 and MV7 wines, giving them rose notes. According to authors such as [PERSON] et al. (2019), 1-hexanol is the result of lipoxygenase activity in the grape and/or aeration of the must. Whatever the case, it fell by 60% as the time before harvesting became longer, probably due to enzyme activity. In addition, [PERSON] et al. (2016) found white wines produced from grapes in early maturity exhibited more intense herbaceous notes than those obtained from riper grapes.