Mariona Gil

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.

Effect of Two Different Treatments for Reducing Grape Yield in Vitis vinifera cv Syrah on Wine Composition and Quality: Berry Thinning versus Cluster Thinning

The influence of two treatments for reducing grape yield, cluster thinning and berry thinning, on red wine composition and quality were studied in a Vitis vinifera cv Syrah vineyard in AOC Penedès (Spain). Cluster thinning reduced grape yield per vine by around 40% whereas berry thinning only reduced it by around 20%. Cluster thinning grapes had higher soluble solids content than control grapes, and their resultant wines have greater anthocyanin and polysaccharide concentrations than the control wine. Wine obtained from berry thinning grapes had a higher total phenolic index, greater flavonol, proanthocyanidin, and polysaccharide concentrations, and lower titratable acidity than the control wine. Wines obtained from both treatments were sufficiently different from the control wine to be significantly distinguished by a trained panel in a triangular test. Even though both treatments seem to be effective at improving the quality of wine, berry thinning has the advantage because it has less impact on crop yield reduction.

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.

Effect of Yeast Strain and Supplementation with Inactive Yeast during Alcoholic Fermentation on Wine Polysaccharides

Polysaccharides appear to exert some sort of positive sensory effect on wine composition. For this reason, attempts have been made to increase their concentration by strategies such as the use of yeast strains with a greater capacity for releasing polysaccharides and supplementation with inactive yeast pretreated to favor the release of polysaccharides. The aim of this study was to determine whether these new strategies are useful for enriching the polysaccharides in red wines. Our results confirm that both strategies provide wines with higher polysaccharide concentrations. Wines fermented with a high polysaccharide-releasing yeast strain had a 32% higher polysaccharide concentration than controls. Wines supplemented with inactive yeasts also had significant increases (11 to 20%) in polysaccharides.

Influence of grape maturity and maceration length on polysaccharide composition of cabernet sauvignon red wines

Cabernet Sauvignon grapes were harvested at three different degrees of maturity (~three, five, and seven weeks postveraison) and used for micro-scale vinifications. For each maturity, four different maceration lengths (one, two, three, and four weeks) were applied in triplicate to assess the influence of both maceration length and grape maturity on the composition of wine polysaccharides. The total concentration of wine polysaccharides was estimated by high resolution size exclusion chromatography-refraction index detection and the polysaccharides then underwent acidic hydrolysis. The neutral monosaccharides released were analyzed by ion exclusion chromatography using an HPLC-RID chromatographic system. The total concentration of wine polysaccharides increases with maceration length and with grape maturity. Both yeast polysaccharides (mannoproteins, MP) and some grape polysaccharides (polysaccharides rich in arabinose and galactose, PRAGs) increase with maceration length. However, grape maturity affects PRAGs and MPs differently: while PRAGs increase with the grape’s maturity, the opposite appears to be true of yeast polysaccharides.

Contribution of yeast and base wine supplementation to sparkling wine composition.

BACKGROUND The differential characteristic of sparkling wine is the formation of foam, which is dependent, among other factors, on yeast autolysis, aging and oenological practices. In this study, we analyzed the effects of yeast strain, nutrient supplementation to the base wine and aging process on the sparkling wine composition and its foamability. RESULTS We determined that the addition of inorganic nitrogen promoted nitrogen liberation to the extracellular medium, while the addition of inactive dry yeast to the base wine caused an increase in the polysaccharide concentration and foaming properties of the sparkling wine. The use of synthetic and natural base wines allowed us to discriminate that the differences in high-molecular-weight polysaccharides and oligosaccharides could be attributed to the yeast cells and that the higher nitrogen content in the natural wine could be due to external proteolysis. CONCLUSION The practices of nitrogen addition and supplementation of inactive dry yeast could modulate the main characteristics of the sparkling wine and be a critical element for the design of this kind of wine.

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.

Study of the changes in volatile compounds, aroma and sensory attributes during the production process of sparkling wine by traditional method

One of the strongest factors that affects the volatile profile of sparkling wine is the winemaking process. Here we focus on determining the effects of the second fermentation and aging on lees of sparkling wine from País grape variety combining different analysis techniques for the first time in sparkling wine: gas chromatography/mass spectrometry/olfactometry and sensorial analysis. During the second fermentation and aging, there was a significant loss of esters that might be related to the adsorption on lees and ester volatility and chemical hydrolysis. The concentration of several compounds such as some esters (diethyl succinate, ethyl lactate, and ethyl isovalerate) increased during aging and could be used as aging markers. Vitispiranes were identified as the best norisoprenoids aging markers for young sparkling wines (12 months of aging). Also, PCA showed that time of aging on lees affected mostly esters and terpenes. On the other hand, the diminution of fruity/floral impact odorants during aging was not perceived in sensorial trials. Our results suggest that the responsibility for fruity/floral nuances in sparkling wine might reside in a few high-impact aromatic compounds, such as ethyl isobutyrate, isoamyl acetate, ethyl hexanoate, β-phenylethanol and diethyl succinate.