RESUMO
The aim of this study was to determine the influence of ion-exchange resin treatments of white grape must for the production of sparkling base wines, on the grape must chemical composition and fermentation kinetics. The experiment included an untreated grape must with a pH of 3.2, and resin-treated musts with pH 3.14, 3.07, and 3.01. Analysis of pH, total acidity, optical density (O.D.) at 420 nm, total phenolic content, tartaric acid, ammonium-nitrogen (AN) and cations (Ca2+, Mg2+, Cu2+, K+, and Na+) was performed. The fermentations were monitored by mass reduction (CO2 release g/L), and fermentation parameters obtained from a modified non-linear sigmoidal equation. The analyses of the musts showed differences in the concentration of metals, total acidity, tartaric acid, AN and O.D. 420 nm. The kinetic parameters of the fermentation showed significant changes between the control must and the ion-exchange treatments. This study showed that the treatment with cationic resins at the tested level significantly affects the chemical composition of the musts, interfering with the fermentation kinetics. In addition, reductions in the must pH index close to 0.1 unit can lead to positive results in the characteristics of the base must of sparkling wines.
RESUMO
The main changes in the volatile profile of base wines and their corresponding sparkling wines produced by traditional method were evaluated and investigated for the first time using headspace solid-phase microextraction combined with comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry detection (GC×GC/TOFMS) and chemometric tools. Fisher ratios helped to find the 119 analytes that were responsible for the main differences between base and sparkling wines and principal component analysis explained 93.1% of the total variance related to the selected 78 compounds. It was also possible to observe five subclusters in base wines and four subclusters in sparkling wines samples through hierarchical cluster analysis, which seemed to have an organised distribution according to the regions where the wines came from. Twenty of the most important volatile compounds co-eluted with other components and separation of some of them was possible due to GC×GC/TOFMS performance.