Estrategias de optimización de la calidad de vinos blancos en la D.O.Ca. Rioja stars

Resumen

In recent years there has been a growing interest in knowing the agronomic behaviour and oenological potential of the white grape varieties authorized in the Rioja Qualified Designation of Origin (D.O.Ca. Rioja). The productive area of these varieties has increased continuously according to market demands since 2013. Currently it is considered of great interest to conserve and revalue traditional varieties and others which, although minority, may represent an added value in the future, providing quality and typicity to wines for their differentiation in an increasingly competitive market. For this reason, it is necessary to carry out studies on the different vineyard management and winemaking techniques to enhance their differential characteristics and increase their quality. The studies included in this research were conducted during three seasons (2018-2020) with four white varieties (Vitis vinifera L.), two of them considered minority varieties, Maturana Blanca and Tempranillo Blanco, and two traditional varieties, Garnacha Blanca and Viura. The aim of this Thesis was to characterize the agronomic and oenological behaviour of these varieties and to evaluate the influence of the application of different agronomic (early and late leaf removal) and oenological (cryomaceration) practices on the final quality of varietal white wines. The results obtained confirmed important differences in the agronomic and oenological behaviour of white varieties studied. The effects of leaf removal were variable depending on the time of application, the variety and the location of the vineyard. This agronomic practice did not significantly affect yield components, except in Tempranillo Blanco, which significantly decreased yield with the early leaf removal treatment. The early leaf removal significantly increased the phenolic content, color parameters and antioxidant activity of the wines; the same changes were observed in late leaf removal but with less intensity. The defoliation treatments wines showed organoleptic characteristics different from the control wines. Sensory discrimination by triangular tests was variable according to the variety. The effects of the application of cryomaceration in the winemaking of white wines have been variable depending on the contact time between the must and the solid parts, the vintage and the variety. In general, this practice decreased the total acidity and tartaric acid content and increased the concentration of malic acid, amino acids, glutathione, varietal aromas and phenolic compounds, in parallel to the cryomaceration time. In Tempranillo Blanco variety the optimum cryomaceration time was estimated at 6 hours. The cryomaceration treatments wines showed organoleptic characteristics different from the control wines. Sensory discrimination by triangular tests was variable according to the vintage and variety. As a general conclusion, based on the results obtained, the choice of variety is one of the main factors to produce higher quality white wines. In general, leaf removal is an agronomic practice that has shown considerable effects on wine quality. On the other hand, cryomaceration is an oenological practice that favors the extraction of the skin components and highlights the varietal character, thus allowing the diversification of wine styles.