Influência de diferentes leveduras na elaboração de vinhos da cv. Riesling Itálico

Abstract

The aromatic complexity of wine in general, and white wine in particular, is what is essential to satisfy an increasingly demanding consumer. Among the most used techniques to achieve this purpose is the addition of yeasts of different genres, thus providing a range of aromatic characteristics that are accentuated in it. In this sense, the objective of this work was to evaluate the use of different strains of yeasts in white wines of Riesling Italic variety, made from grapes grown in the Serra Gaúcha region, in the state of Rio Grande do Sul. To carry out the study, 100 liters of must already sulfited with 72 mg.L-1 of SO2 were received in the experimental winery of the Federal University of Pampa, Campus Dom Pedrito (RS), each of them fractionated in 5 treatments with 3 replicates. The yeasts, randomly distributed, were inoculated in the treatments, being three yeasts of the genus Saccharomyces with different purposes: in Treatment 1 (T1) Saccharomyces cerevisiae of thiols; in Treatment 2 (T2) Saccharomyces cerevisiae cerevisiae ester-forming, and in Treatment 3 (T3), a Saccharomyces bayanus. In addition, two non-Saccharomyces yeasts were inoculated, from which a significant contribution was expected in the production of fruity esters, high purity and low production of volatile acidity, being Torulaspora delbrueckii Treatment 4 (T4) and Metschnikowa pulcherrima in the Treatment 5 (T5). All alcoholic fermentation was conducted under temperature control at 15 ° C. The quality of the must, taking into account the total sugars (167.6 g.L-1), total acidity (81 meq.L-1) and pH (3,5), were within normal standards for grapes of the Riesling variety cultivated in the region of the Serra Gaúcha. However, to improve the quality of the wines, all treatments were chaptalizated, with the addition of 18 g.L-1 of sugar. Based on the results, it was possible to observe that there were no significant differences between the treatments in relation to the variables pH, total acidity and alcoholic degree. However, with respect to the fermentation yield, T3 was the treatment that obtained the best performance, reaching the ideal density (below 1.000 g.cm-3) in the course of 6 to 7 days, followed by treatments T1 and T5 (7 to 8 days), with treatments T2 and T4, which had the lowest performance (9 to 10 days). The T4 treatment was also the one that presented a higher amount of residual sugars, which proves the less activity of this yeast in more alcoholic means. All the yeasts used have a low production of volatile acidity, but the lowest concentration was Saccharomyces cerevisiae cerevisiae, used in treatment T2 (0.1 g.L1), and the other treatments presented higher concentrations (0.4 to 0.5 g.L-1), although it is still within the parameters considered ideal for obtaining quality white wines. T2 was also the treatment with lower concentrations of glycerol (5.1 g.L-1). This compound is mainly formed by glycerirubic fermentation through the metabolism of yeasts at the beginning of alcoholic fermentation, usually being produced by the first 50 grams of fermented sugars, which may indicate a greater activity of this yeast in this fermentation period. In relation to volatile compounds and sensorial analyzes, T1 treatment was the one that obtained the best results, with very similar aspects to the T5 treatment, where they presented a better flavor intensity, higher floral notes, citrus fruits and white pulp, besides a better gustatory quality and a greater overall impression. In general, we can say that all the yeasts used have the potential to produce quality white wines, since they had good fermentation yields, satisfactory production of alcohol and glycerol, and low production of volatile acidity.