# Part II--Aroma Profile of Twenty White Grapevine Varieties: A Chemotaxonomic Marker Approach
## 3 Results & Discussion
### Volatile Composition
#### 3.3.1 Free Volatile Fraction
In this research, they were detected almost exclusively in the free aromatic form of almost every variety studied (Figure 1), except in 'Blanca de Monterrei', 'Palomino', 'Pirixileira' and 'Treixadura'. 'Batoca', 'Ratino' and 'Silveirina' were those varieties with the highest content, with \(\beta\)-damascenone as the major content one in the last two varieties, suggested as a fruity aroma-enhancer in some studies [59]. Other studies identify it as a high-flaval-intensity compound [60]. Organic acids together with other families, such as terpenoids, thiol precursors and esters, among others, are one of the most important families of aromatic compounds [61]. Figure 1 reflects this previous information, with acids appearing in both free and glycosidicfractions in every variety studied, representing up to 25% of the free aromatic profile of the varieties studied, with 'Planta Fina' being the variety in which they have the greatest contribution in their free form, followed by 'Godello', 'Jarrosuelto' and 'Torrontes', with up to 20%. They are characterized by fatty and cheesly smells, and they are partly related to the generic vinous character of the wine [62]. As it was previously mentioned, 'Planta Fina' stood out based on its high content, with hexanoic acid as the major compound, such as for 'Agudelo', 'Albilla do Avia', 'Batoca', 'Branco Lexitmo', 'Fernao Pires', 'Garrido Fino', 'Godello', 'Lado', 'Prixileira' and 'Ratino'. C\({}_{6}\) compounds are broadly described as having characteristic odors of green, grass and vegetation. C\({}_{6}\) alcohols derived from grapes were tested to serve as varietal markers [63]. Six carbon alcohols and aldehydes have been identified as the major compounds in the free fraction of several Spanish varieties [64], as has also been observed in this study, being detected as the main contributing family in the free aromatic profile of every variety studied, accounting for more than 40% of the free aromatic fraction, except for 'Fernao Pires', 'Italia', 'Moscatel de Bago Muldo' and 'Torrontes' (Figure 1). Concentrations ranged from 4481 ug\(\cdot\)L\({}^{-1}\) in 'Ratino' to 734 ug\(\cdot\)L\({}^{-1}\) in 'Torrontes'. Hexanol and 2-hexenal were two of the major compounds detected with descriptors, such as resin, flower, green and apple and green in the second compound [40; 54], being also some of the major compounds found in other studies [26], being classified in that work as alcohols and aldehydes, resulting these families the major compounds detected in that study. Alcohols were detected and semi-quantified in high contents as have already been found in other studies [65]. In this study, similar percentage contributions to the aromatic profile of each studied variety were detected in both free and glycosidic fractions, with a slightly higher percentage in the glycosidic fraction in every variety (Figure 1). 'Albilla do Avia' and 'Italia' could be highlighted for having the lowest amounts of alcohol compared to the rest of varieties studied, with 2-ethyl-1-hexanol, as the major compound in every variety, being also the major compound identified in the free fraction of varieties studied in [36; 37], characterized by having fresh, floral, citrus, and sweet aroma descriptors [66]. Aldehydes are organic compounds that are very commonly found in food or flavoring agents and usually have a low odor threshold [67]. In this study, they were detected in lower quantities compared with C\({}_{6}\) compounds and alcohols, with 'Godello' showing the highest content (167 ug\(\cdot\)L\({}^{-1}\)) and 'Italia' and 'Prixileira' the lowest one (28 ug\(\cdot\)L\({}^{-1}\)). They also had a low percentage contribution to the free, aromatic fraction, with a maximum of 5% in the 'Godello' free aromatic profile (Figure 1). Esters are one of the main aromatic family compounds related to the fruity aroma of wines [62].