Study of the volatil profile of minority white varieties

Abstract

The genetic material preservation is a priority issue in winemaking research. The recovery of minority grape varieties can control the genetic erosion, contributing also to preserve wine typical characteristics. In D.O.Ca. Rioja (Spain) the number of grown white varieties has been very limited, representing Viura the 91% of the cultivated white grape area in 2005, while the others, Garnacha Blanca and Malvasía riojana, hardly were grown. For this reason, a recovery and characterization study of plant material was carried out in this region. In 2008, the results obtained allowed the authorization of three minority white varieties: Tempranillo Blanco, Maturana Blanca and Turruntés. Tempranillo Blanco comes from a mutation of Tempranillo Tinto and it was picked up for the first time in La Rioja in 1988. Maturana Blanca and Turruntés have been grown since long time ago and were recovered from old vineyards. Tempranillo Blanco and Maturana Blanca are only authorized in D.O.Ca. Rioja, and therefore they can really contribute to wines differentiation, increasing the added value and providing wines with personal and marked characteristics. Turruntés, that is a synonym of Albillo Mayor, is cultivated in other Spanish regions. The variety is one of the main factors responsible for the must and wine aroma. In this study, the pre-fermentative volatile profile of five minority white varieties was determined during the 2014 vintage, in comparison to Viura, considering it as the reference variety. All the cultivars were grown in an experimental vineyard. The volatile compounds of these varieties were analyzed by HS-SPME-GC-MS. The results showed marked differences in the aromatic profile of the studied grape varieties. In all cases, C6 were the most abundant compounds (70 – 93%), followed by norisoprenoids (4 – 13%), carbonyl (0.6 – 4%), benzenoids (0.1 – 4%) and terpenoids (1.2 – 3.3%). Cv. Tempranillo Blanco highlighted by a high content of C6 compounds, greater than cv. Malvasía, Turruntés and Viura. The most representative compounds were hexanal and (E)-2-hexenal. Within norisoprenoids, (E)-β-damascenone and (Z)-β-damascenone were the most abundant compounds in cv. Garnacha Blanca and Malvasía. In these varieties a higher content of terpenoids, such as trans-geranyl-acetone, β-linalool and nerol oxide was observed. Both, norisoprenoids and terpenoids are the most odoriferous groups of compounds, with floral scents that play a key role in the varietal aroma. The content of benzenoids in cv. Malvasía and cv. Turruntés was higher than in the rest of varieties, being 2-phenylethanol the most important molecule. Tempranillo Blanco and Garnacha Blanca presented a significantly higher global aromatic content than Turruntés and Viura. Thus, minority white grape varieties can provide wines with interesting and marked aromatic characteristics.