Estudios sobre la influencia de distintas técnicas de crianza en la capacidad antirradicalaria y en la composición volátil de vinos tintos

Resumen

RESUMEN DE LA TESIS DOCTORAL DE D./Da Georgiana-Diana Dumitriu (Gabur) STUDIES REGARDING THE INFLUENCE OF AGEING TECHNIQUES ON THE ANTIRADICAL CAPACITY AND VOLATILE COMPOUNDS OF RED WINE 1. Introduction One of the most important practices in the winemaking is the maturation process, where a series of physical, chemical and biological changes take place that improve wines stability and also modification to the compositional and organoleptic characteristics. Traditional maturation is costly, requires long periods of time, storage cellar and also a proper maintenance. This has prompted the development of alternative maturation systems, simpler and more accessible, such as the use of fragments of oak, known as oak chips that accelerate the maturation process, reduce costs and at the same time, retain wine quality. The final product is determined not only by the different characteristics of the oak fragments added, such as origin, size, toasting process, but also by the dosage used and the time of contact with the wine. 2. Content and conclussion This paper includes a comprehensive study on the antioxidant activity and volatile compounds of local wines (Fetească neagră) aged for 1.5 to 3 months by traditional process (barrel) and alternative processes (stave and chips). General trends observed in chemical parameters changes were similar for red wines maturated using traditional methods (barrels) and alternative (staves and chips). In the present experiment, using the traditional maturation method (barrels) and two alternative methods (staves and chips) were identified seven aromatic compounds (key) from three different chemical classes: furan compounds (furfural, 5-methylfurfural and 5-hydroxymethylfurfural), volatile phenols (guaiacol and 4-vinylguaiacol) and wood compounds (trans-whiskey lactone and cis-whiskey lactone). Multivariate analysis of variance (MANOVA) was performed in order to determine which factors had a statistically significant effect on concentrations of volatile compounds of maturated wine samples and to assess the importance of interactions between factors. It clearly showed very significant statistically influence exerted by the tested factors (maturation duration – T, toasting degree – GP and dose – D, for chips samples). Two discriminant analyses have been made to determine the differences between the wines due to maturation processes. For the classification of wines produced were used in the first study values of majority and minority volatile compunds, and in the second values of antioxidant activity and their phenolic fractions. In both studies there is a clear differentiation of all maturation processes, forming four groups that include the control samples, variants with alternative processes (staves and chips) and variant matured by the traditional method (barrel). A cluster analysis was performed, and to classify the obtained variables were used volatile compounds values. Following this statistical analysis, both at 1.5 and 3 months have formed two groups: the first contains wines with staves, chips and control sample, while the second group includes only wines matured in barrels. The aromatic profile of Fetească neagră wines included chemical, fatty, citrus, fruit, butter, floral, vegetable, roasted, spice and wood series. Wines matured through alternative maturation processes (staves and chips) have similar OAV, while wines maturated traditional differs from the alternative ones throw smaller chemical, fruit and fatty acids series and larger citrus, wood, toasted and spice series. Of the three maturation processes, the highest content of phenolic compounds for unfractionated samples is recorded in wines maturated with staves for three months. The total antioxidant activity of unfractionated samples decreased for control samples maturated three months, however, was constant in wines maturated with medium plus chips and increased in all other variants. From all maturation processes, the highest values recorded for total antioxidant activity are in variants that used medium and medium plus barrels. Phenolic fractions are represented by phenolic acids (fraction 1) and flavanols (fraction 2) that decrease according to time for wines maturated with chips and increase for samples maturated with staves and barrels, while flavonols (fraction 3), anthocyanins and procyanidins (fraction 4), having high molecular weight increase in all types of maturation. Chromatic characteristics are influenced by the maturation process used. The wines aged with 5 g/L of chips with a medium plus and heavy toasting level were more brownish than the same wines aged with 3 g/L of chips. Examining the three maturation processes, wines matured in barrels had a less saturated color than wines aged with staves and chips. All wine samples have low lightness, which is linked to the maceration process during fermentation and to the formation of color pigments during maturation. The most intensely colored wines were obtained by maturation with low toasted chips, and most tinted were obtained for barrel maturation. Summarizing, a deep study of wine produced with the grape variety “Fetească neagră” has been carried and several aging alternatives has been proposed. The results can help the winemaker to choose an ageing procedure in function of the type of wine they want to produced.