Comparison of a Rapid Light-Induced and Forced Test to Study the Oxidative Stability of White Wines

The oxidation processes of white wines can occur during storage and commercialization due to several factors, and these can negatively affect the color, aroma, and quality of the wine. Wineries should have faster and simpler methods that provide valuable information on oxidation stability of wines and allow fast decision-making procedures, able to trigger suitable technological interventions. Using a portable prototype instrument for light irradiations at different wavelengths and times was considered and evaluated on sensorial, spectrophotometric, and colorimetric parameters of white wines. The sensorial analysis revealed that white and light blue were the most significant, after only 1 h of irradiation. The experimental results showed that hydrogen peroxide could enhance the effect of light treatment, allowing a contemporary evaluation of the oxidation stability of wine against light and chemical stresses. As expected, a good correlation (R2 > 0.89) between optical density at 420 nm and b* parameter was highlighted. The synergic effect of light and H2O2 was also studied on the hydrolyzable and condensed tannins’ additions to white wine. The proposed methodology could be used to evaluate the oxidative stability of white wines, but also to evaluate the effect of some oenological adjuvants on wine stability.

Medium chain fatty acids and fatty acid esters as potential markers of alcoholic fermentation of white wines

Aroma components of wines play an important role in the sensory quality of wines. In our paper we investigate the effect of commercially available yeast nutrients under different fermentation parameters. Caproic acid, caprylic acid, capric acid, and different fatty acid esters were used as markers of the alcoholic fermentation process. The optimal temperature for the fermentation of different white wines was at 15–16 °C, in the case of examined wines lower concentrations of fatty acids and fatty acid esters were found at this temperature. At 25–26 °C fermentation temperature very high concentrations of fatty acids and fatty acid esters were detected. Applying different nitrogen-containing wine additives we managed to achieve better aroma profiles for white wines even using musts of lower quality.

Transfer of Macronutrients, Micronutrients, and Toxic Elements from Soil to Grapes to White Wines in Uncontaminated Vineyards

Wine is a popular beverage and may be a source of nutrient and toxic elements during human consumption. Here, we explored the variation in nutrient and toxic elements from soils to grape berries and commercial white wines (Chardonnay) at five USA vineyards (New York, Vermont, California, Virginia) with strongly contrasting geology, soils, and climates. Samples were analyzed for macronutrients (Ca, K, and Mg), micronutrients (Mn, Cu, and Zn), and toxic elements (As, Cd, and Pb). Our study showed contrasting macronutrient, micronutrient, and toxic element concentrations in soils and in vines, leaves, and grapes. However, plant tissue concentrations did not correspond with total soil concentrations, suggesting a disconnect governing their accumulation. Bioconcentration factors for soil to grape berry transfer suggest the accumulation of Ca, K and Mg in berries while Fe, Mn, Cu, Zn, and Pb were generally not accumulated in our study or in previous studies. Wines from the five vineyards studied had comparable nutrient, micronutrient, and toxic metal concentrations as wines from Germany, Italy, Portugal, Spain, Croatia, Czech Republic, and Japan. The transfer of nutrients and toxic elements from grape berries to wine indicated that only Ca, K, and Mg were added or retained while concentrations of all other micronutrients and toxic elements were somewhat to extensively diminished. Thus, there appears to be a substantial effect on the geochemistry of the wine from the grape from either the fermentation process (i.e., flocculation), or a dilution effect. We conclude that soils, geology, and climate do not appear to generate a unique geochemical terroir as the transfer and concentration of inorganic nutrients appear to be comparable across strongly contrasting vineyards. This has several implications for human health. Nutrients in wine have potential impacts for human nutrition, as wine can meet or exceed the recommended dietary requirements of Ca, K, Mg, and Fe, and toxic metals As and Pb concentrations were also non-trivial.

Chemical Composition of White Wines Produced from Different Grape Varieties and Wine Regions in Slovakia

In this work, chemical parameters such as sugar (glucose and fructose) content, organic acid (total acids, malic and tartaric acids), total phenolic content and the antioxidant activity of 12 white wines (chardonnay, pinot blanc and pinot gris) from various wine regions in Slovakia were studied in order to identify differences among the varieties and wine-growing regions. The wine samples were examined by Fourier-transform infrared spectroscopy (FTIR) and UV-VIS spectrophotometry (for determination of total polyphenolic content (TPC) and total antioxidant activity (TAA)) methods. Content of alcohol ranged between 11.50% and 13.80% with the mean value 12.52%. Mean content of total acids varied between 4.63 ± 0.09 and 6.63 ± 0.05 g.L−1, tartaric acid varied between 1.62 ± 0.09 and 2.93 ± 0.03 g L−1, malic acid was found in the concentrations ranged from 0.07 ± 0.05 and 2.50 ± 0.08 g L−1 and lactic acid was present between 1.53 and 0.01 g L−1. The content of fructose was, in general, higher in the samples from the Južnoslovenská and Nitrianska wine regions and glucose was higher in the Malokarpatská wine region. Chardonnay wines showed the highest content of total polyphenols and the antioxidant activity in the samples ranged from 51.06 ± 027 to 72.53 ± 0.35% inhibition of DPPH. The PCA analysis based on chemical descriptors distinguished the Nitrianska and Stredoslovenská wine regions. According to similarities among the wine samples, four main classes were formed by cluster analysis.

Antioxidant activity and resveratrol content in wines the national origin

Wines are an important source of resveratrol and polyphenols, in this sense this work has focused on the determination of antioxidant activity and resveratrol content in wines of origin. The different wines analyzed exhibited strong antioxidant activity for the ABTS and DPPH tests, which are in the ranges of 2.123 to 25.097 [µmol/ml] and 2.348 to 17.138 [µmol/ml] for red wines respectively, while for white wines the ranges they are 0.793 to 2.604 [µmol/ml] and 0.419 to 3.07 [µmol/ml] respectively. Regarding the quantification and presence of trans-resveratrol, this was confirmed in most of the wines analyzed, with concentrations ranging between 0.77 and 3.25 [ppm] in red wines. As for white wines, these oscillate in the range of 0.18 to 0.69 [ppm]. Analyzing and comparing the results obtained in wines of origin, we observe that red wines have a good content of resveratrol and that in turn comparing results of other authors, we observe that the content of resveratrol in wines of origin is within the bibliographic range, both for red and white wines.