The effect of supplementation with three commercial inactive dry yeasts on the colour, phenolic compounds, polysaccharides and astringency of a model wine solution and red wine.

BACKGROUND: Nowadays supplementing red wines with commercial inactive dry yeasts is a widespread practice in winemaking because it leads to better balanced wines through increased mouthfeel and smooth astringency. The aim of this article is to study, in a red wine and in a model wine solution, how supplementation with three commercial inactive dry yeasts affects chemical composition and astringency. This will give us a better understanding of the action mechanism involved. RESULTS: The results suggest that this action mechanism is related to two different phenomena. The first is that inactive yeasts release polysaccharides and oligosaccharides which can increase mouthfeel and inhibit interactions between salivary protein and tannins. The second is that they have a direct effect on the precipitation or absorption of proanthocyanidins, especially the larger polymers, which have been described as the most astringent. CONCLUSION: It can be concluded that supplementation with inactive yeasts is indeed a useful tool for smoothing the astringency of red wines. © 2016 Society of Chemical Industry.

Influence of grape maturity on the foaming properties of base wines and sparkling wines (Cava).

BACKGROUND: The aim of this paper is to determine the main factors that influence the foaming properties of base wines and sparkling wines and, in particular, the role played by the maturity of the grapes in the controlled designation of origin (CDO) Cava. Macabeo, Xarel.lo, Parellada and Chardonnay grapes were harvested at two different maturity levels in two vintages. The first harvest was selected because of its desirable titratable acidity and the second because of its optimal sugar concentration. The mono-varietal base wines and standard blends were transformed into sparkling wines and aged for 14 months. RESULTS: The results indicate that the main factors affecting foam properties are ethanol content, high molecular weight polysaccharides and gluconic acid (which have a negative effect), and proteins (which have a positive effect). CONCLUSION: The main conclusion of this study is that the foaming properties of wines can be improved if harvest dates are advanced.

Influence of grape maturity and maceration length on color, polyphenolic composition, and polysaccharide content of Cabernet Sauvignon and Tempranillo wines.

The aim of this paper was to study how maturity and maceration length affect color, phenolic compounds, polysaccharides, and sensorial quality of Cabernet Sauvignon and Tempranillo wines at three stages of grape ripening. Ripeness increased color extractability, phenolic compounds, and polysaccharide concentrations. Moreover, the proanthocyanidin mean degree of polymerization (mDP) and the percentage of prodelphinidins also increased with maturity, whereas the percentage of galloylation decreased. In general, wines from riper grapes contain higher proportions of skin proanthocyanidins. Color and anthocyanin concentration decreased when the maceration was longer, whereas polysaccharide and proanthocyanidin concentrations did the opposite. It was also detected that the mDP and the percentage of prodelphinidins decreased when the maceration was extended, whereas the percentage of galloylation increased. These data seem to indicate that proanthocyanidin extraction from seeds is clearly increased throughout the maceration time.

Influence of wine pH on changes in color and polyphenol composition induced by micro-oxygenation.

The presence of oxygen in red wine leads to the transformation of ethanol into ethanal, which after capturing a proton will react with flavanols to start the process of forming ethyl bridges between flavanols and between flavanols and anthocyanins. Wine pH also conditions the equilibrium between the different anthocyanin structures and may thus affect anthocyanin reactivity. Consequently, the aim of this paper was to study how the pH can affect the changes induced by micro-oxygenation in two wines with different phenolic composition. The differences between micro-oxygenated wines and their controls were, in general, greater when the pH was more acidic. Specifically, the differences between micro-oxygenated wines and their corresponding controls in terms of color intensity, anthocyanin concentration, PVPP index, ethyl-linked pigments, B-type vitisins, polymeric pigments, and ethylidene-bridged flavanols were greater at lower pH. In contrast, the effects of micro-oxygenation when the pH was less acidic were much less evident and sometimes practically nonexistent. These results demonstrate for the first time that the pH of the wine has a great influence on oxygen-induced changes of color and phenolic compounds.

Comparison of methods for estimating phenolic maturity in grapes: correlation between predicted and obtained parameters.

With the aim of determining the real predictive ability of three methods for measuring phenolic maturity (Glories, ITV and Cromoenos), representative grapes of Merlot, Cabernet sauvignon, Grenache and Tempranillo were harvested at three different ripening levels. The grapes were vinified by triplicate and were also used for phenolic maturity estimation. After that, color intensity, CIELAB coordinates, anthocyanins by spectrometry and HPLC and total phenolics were analysed in wines and also in the different extracts from the three extraction methods. Statistical analysis of data was carried out to determine the real performance of prediction of the different methods. Glories method predicted reasonably the color intensity, CIELAB coordinates and the concentration of anthocyanins and total phenolics in wine although it needs a lot of time and it requires working carefully. On the other hand, Cromoenos method predicted similarly or even better the color and phenolic composition of wine. This method also presents the advantage of being much faster and easier to apply. In contrast, although the ITV method provided reasonable results for anthocyanins and total phenolic compounds its color prediction was not adequate.