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 Seeds and Stems on Wine Composition and Astringency.

The aim of this paper is to study the real influence of seeds and stems on wine composition, astringency, and bitterness. A decolored grape juice and a grape juice macerated for 4 days from the same Cabernet Sauvignon grapes were fermented with or without supplementation with 100% seeds, 300% seeds, or 100% stems. Once alcoholic fermentation had finished, the wines were analyzed and tasted. The presence of seeds and stems increased the concentration of flavan-3-ol monomers with respect to the controls. However, the seeds mainly released (+)-catechin and (-)-epicatechin, whereas the stems mainly released (+)-catechin and (+)-gallocatechin. The seeds and stems also released proanthocyanidins; those from seeds have a lower mDP and a high percentage of galloylation, whereas those from stems have a higher mDP and a relatively high percentage of prodelphinidins. The presence of seeds and stems brought about a slight but significant increase in pH and lowered titratable acidity and ethanol content. The presence of seeds boosted color intensity, whereas stems had the opposite effect. Finally, both seeds and stems increased wine astringency and bitterness.

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.