Water stress and ripeness effects on the volatile composition of Cabernet Sauvignon wines.

BACKGROUND: Controlled water deficits affect grape berry physiology and the resulting wines, with volatile composition being the one of the affected parameters. However, there is a potential disconnect between aromatic maturity and sugar accumulation. Accordingly, the effects of three different water status levels over two growing seasons (2014 and 2015) and two different harvest dates on the aroma compounds from Cabernet Sauvignon wines were studied. Volatile compounds were determined using headspace solid phase microextraction coupled with gas chromatoghraphy/mass spectrometry. RESULTS: Around 45 volatile compounds were determined in the wines and, among these, esters were affected the most, presenting lower concentrations when the most restrictive water treatment was applied in both years. By contrast, volatile acids presented the highest concentrations when the lowest level of irrigation was applied. On the other hand, a delay in harvesting produced an increase in the total amount of volatile compounds in samples from the most restrictive water treatment. These results are coincident with a principal component analysis that indicated a great separation between years, deficit irrigation treatments and harvest dates. CONCLUSION: The results of the present study suggest that a low water supply had a negative effect on the aromatic potential of wines at a similar ripening stage. However, this effect could be countered by harvesting at a later date. © 2017 Society of Chemical Industry.

Controlled water deficit during ripening affects proanthocyanidin synthesis, concentration and composition in Cabernet Sauvignon grape skins.

The influence of controlled water deficit on the phenolic composition and gene expression of VvLAR2, VvMYBPA1, VvMYBPA2 and VvMYB4a in Cabernet Sauvignon grape skins throughout ripening was investigated. The assay was carried out on own-rooted Vitis vinifera plants cv. Cabernet Sauvignon in a commercial vineyard from veraison until commercial harvest. Three irrigation regimes were used from veraison until harvest with the following treatments: T1: 3.6 mm day-1; T2: 1.8 mm day-1 and T3: 0.3 mm day-1. The content of total phenols and total anthocyanins in grape skins increased during ripening, but water deficit did not produce differences among treatments in the total anthocyanin concentration. Proanthocyanidins (PAs) decreased throughout ripening, although approximately 25 days after veraison (DAV), their content slightly increased. This effect was more pronounced in the most restrictive treatment (T3). A similar pattern was observed in the transcript abundance of VvLAR2, VvMYBPA1 and VvMYB4a. PAs separation revealed differences in concentration but not in the proportion among fractions among the irrigation treatments. Additionally, controlled water deficit increased the mean degree of polymerization and the flavan-3-ol polymeric concentration in grape skins throughout ripening but with no effects on the extent of PAs galloylation. Our results suggest that the water status of Cabernet Sauvignon grapevines affects the gene expression for proteins involved in the synthesis of PAs, increasing their concentration and also their composition, with further evidence for the efficacy of a convenient, controlled water deficit strategy for grapevine cultivation.

Effect of selected Saccharomyces cerevisiae yeast strains and different aging techniques on the polysaccharide and polyphenolic composition and sensorial characteristics of Cabernet Sauvignon red wines.

BACKGROUND: The objective of this work was to study the effect of two Saccharomyces cerevisiae yeast strains with different capabilities of polysaccharide liberation during alcoholic fermentation in addition to subsequent aging on lees with or without oak wood chips as well as aging with commercial inactive dry yeast on the physical, chemical and sensorial characteristics of Cabernet Sauvignon red wines. RESULTS: The HPS (high levels of polysaccharides) yeast strain released higher amounts of polysaccharides (429 g L(-1)) than EC1118 (390 g L(-1)) during alcoholic fermentation, but the concentration equalized during the aging period (424 and 417 g L(-1) respectively). All aging techniques increased the polysaccharide concentration, but the increase was dependent on the technique applied. A higher liberation of polysaccharides reduced the concentration of most of the phenolic families analyzed. Moreover, no clear effect of the different aging techniques used in this study on color stabilization was found. The HPS wines were better valued than the EC1118 wines by the panel of tasters after alcoholic fermentation. CONCLUSION: In general, the HPS wines showed better physicochemical and sensorial characteristics than the EC1118 wines. According to the results obtained during the aging period, all aging techniques contributed to improve wine quality, but it was difficult to establish the technique that allowed the best wine to be obtained, because it depended on the aging technique used and the period of aging.

Chemical and sensory effects of storing sauvignon Blanc wine in colored bottles under artificial light.

The chemical and sensory effects of storing Sauvignon Blanc in colored bottles and exposing them to artificial light were examined. The colors of the bottles chosen were Dead Leaf Green, Antique Green, Amber, and Flint. The light was provided by fluorescent tubes with a regime of 16 h of exposure during 8 months of storage. The results indicated that the wine's chemical composition was affected by the type of bottle used. The Flint bottle presented the lowest concentration of total phenols. Yellow coloration was not dependent on the bottle color, as the wine in darker bottles (Amber, Antique Green, and Dead Leaf Green) had considerably more yellow color development than the wine in clear bottles. With regard to the sensory analyses performed, a trend showing an increase in color intensity and a decrease in overall aromas depending on the bottle color was observed. The wine's aromatic description changed significantly during its storage under artificial light conditions, demonstrating a decrease in vegetal aromas and an increase in citrus and tropical flavors that was dependent on the bottle color.

Phenolic composition and mouthfeel characteristics resulting from blending Chilean red wines.

BACKGROUND: The blending of wine is a common practice in winemaking to improve certain characteristics that are appreciated by consumers. The use of some cultivars may contribute phenolic compounds that modify certain characteristics in blended wines, particularly those related to mouthfeel. The aim of this work was to study the effect of Carménère, Merlot and Cabernet Franc on the phenolic composition, proanthocyanidin profile and mouthfeel characteristics of Cabernet Sauvignon blends. RESULTS: Significant differences in chemical composition were observed among the monovarietal wines. Separation using Sep-Pak C18 cartridges revealed differences in the concentration but not in the proportion of various proanthocyanidins. Blending reduced polyphenol concentration differences among the various monovarietal wines. Although no major overall differences were observed after blending the monovarietal wines, this oenological practice produced clear differences in mouthfeel characteristics in such a way that the quality of the perceived astringency was different. CONCLUSION: This study showed that the use of a particular wine variety (Cabernet Sauvignon) in a higher proportion in wine blending produced blends that were less differentiable from the monovarietal wine, owing to a suppression effect, producing an apparent standardization of the wines regarding chemical composition.

Effect of inert gas and prefermentative treatment with polyvinylpolypyrrolidone on the phenolic composition of Chilean Sauvignon blanc wines.

BACKGROUND: Sauvignon blanc wines are produced under a wide variety of winemaking conditions, some of which include different fruit-ripening levels, cold soaks and the use of fining agents and inert gases. Anecdotal evidence suggests that sensory variations among these wines may have to do with their phenolic composition and concentration. Therefore the aim of this work was to study the effects of different winemaking conditions typically used in Chile on the phenolic composition and concentration of Sauvignon blanc wines. RESULTS: The use of an inert gas (CO2) in winemaking produced differences in the proportion of proanthocyanidin fractions. A higher concentration of flavan-3-ol monomers resulted from winemaking in the presence of inert gas. This condition also produced a higher content of total phenols and low-molecular-weight phenolic compounds. Low doses of polyvinylpolypyrrolidone (PVPP) in the prefermentative treatments produced wines with a higher content of phenolic compounds. Under these conditions a higher content of polymeric proanthocyanidins was observed. CONCLUSION: Different winemaking conditions modified the concentration and proportion of proanthocyanidin fractions and the global phenolic composition of the resulting white wines. This should be taken into account by the wineries producing these wines.