Utilização de resina de troca iônica pré-fermentativa para elaborar vinhos base de espumantes

Abstract

Considering that sparkling wines are important products for the Brazilian wine sector, researches related to different elaboration techniques are relevant for the increase of enological options and product diversity. The acidity of wines is usually corrected during the process of elaboration with organic acids, but currently there are other alternatives that are being tested and used in order to improve the quality of the product. Among these alternatives are the cation exchange resins recommended for enological applications are constituted by a matrix of polystyrene reticulated with divinylbenzene. These resins are encapsulated in microspheres from 0.3 to 1.2 mm, and have high physic-chemical stability. After an acid treatment, the resins are positively charged with H+ and exchange these cations with K+, Ca2+ and other cations present in grape must, releasing tartaric and other acids, reducing the pH. These chemical modifications may affect the chemical composition of must, wines and also yeast metabolism. In view of this, the purpose of this work was to analyze, gather and interpret data and information evaluating the impact of the technique on fermentative kinetics, on the chemical characteristics of musts and on the chemical and organoleptic characteristics of the resulting wines, from a same must, with different times of passage through a commercial cation exchange resins, specific for enological use. For the experiments, a Chardonnay must (75 L) was obtained by pneumatic press extraction, and clarified with silica and gelatin. The must passed through a resin column, as many times as necessary to obtain the desired pH reductions. The experiment treatments included the control must with pH index 3.2, and must with pH 3.14, 3.07, 3.01, and 2.92, obtained by cation-exchange resin treatment. All the musts were inoculated with the same commercial yeast strain (20 g/hL), and fermentation was monitored by mass reduction (CO2 release (g/L)). Kinetic data were adjusted by a modified non-linear sigmoidal equation of Gompertz, and expressed as: Lag-phase duration (Lag=hours), total CO2 release (Ymax=g/L) and maximum rate of CO2 release (µmax=g/L/day). Musts analyses included the measured of pH, total acidity, color, total polyphenols, tartaric acid, ammoniacal nitrogen and metals (cations). There were basic analysis made in the wine and also volatile compounds, organoleptic and oxidation within time (measured by the samples’ color change). The kinetic parameters showed significant differences among the control and the other treatments, except for the treatment with pH of 2,93, which had a higher total CO2 release. The reductions of the three parameters was linear (r>95) on the pH range of 3,2 and 3,01. However, at the lowest pHs (3.01 and 2.93) the differences were not significant. Must analyses showed significant differences following the tendency from the resin’s operation for cation’s reduction, increase of total acidity, and concentration of free tartaric acid. The amount of ammoniacal nitrogen had a significant decrease on the treatments. Some wine volatile compounds concentration exhibited significant differences between treatments, leading to an increase in higher alcohols concentration, and a decrease in acetate and ethylic esters. The oxidation of wines was accompanied through time and showed a major resistance on the wines with altered pH. In the organoleptic analysis, there was a preference for the control wine and the wines with similar pH to the control. This study shows that the treatment with cationic resins affects the fermentation, must and wines and it can contribute in a positive or negative way, depending on the treatment, for base-wine production.