Changes in phytochemical composition of Merlot grape and wine induced by the direct application of boron.

In this study the effect of the direct application of different concentrations of boron in grape bunches on the phytochemical composition of grapes and wine was evaluated. The experiment was carried out by direct application to the grape bunch of different concentrations (0, 1.0, 2.0, 4.0 and 8.0 g/L) of boron solution, in two consecutive vintages, 2018 and 2019. The wines were elaborated by the same microvinification method. Histological analyzes by optical microscopy and phenolic profile by HPLC-DAD were performed on the grapes. The wines were analyzed by HPLC-DAD and ICP-MS for phenolic profile and elemental composition, respectively. Histological analyzes of the grape skin showed an increase in the presence of polyphenols in the cellular tissue of grapes treated with different concentrations of boron when compared to the control samples in both vintages. The addition of boron influenced the phenolic profile of the grapes, resulting in an increase in the content of anthocyanins and flavanols. Regarding to wines, the treatment of grapes by direct application of boron significantly influenced the chemical composition of wines. In 2018, the application of 2 g/L of boron showed a significant increase in the concentration of malvidin and delphinidin in wines. The application of 1 g/L showed the highest concentration of malvidin, delphinidin and peonidin in the 2019 vintage. The boron content increased in the wine samples according to the boron concentrations applied to the grape. Thus, it is possible to produce chemically distinct wines with the direct application of boron to the grapes.

Polyphenolic Profiling, Browning, and Glutathione Content of Sparkling Wines Produced with Nontraditional Grape Varieties: Indicator of Quality During the Biological Aging.

Sparkling wines were elaborated with the nontraditional varieties Villenave, Niagara, Manzoni, and Goethe, and monitored in relation to the changes in phenolic composition, browning index, and glutathione content during 18 months of biological aging (sur lies). Important changes in the phenolic profile, browning index, and glutathione content were observed in the sparkling wines during the over-lees aging period. The major phenolic compound in the sparkling wines was tyrosol, followed by caffeic, trans-caftaric, and gallic acids, catechin and epicatechin. The biological aging led to an increase in the individual phenolic compounds, especially caffeic, gallic, and ellagic acids, and an increase in the browning index was also observed during the aging period. Caffeic acid was significantly correlated with browning and aging period in all sparkling wines, which indicates that this compound can be useful as a quality marker to monitoring the biological aging profile of white sparkling wines. The results obtained indicate that the aging period (sur lie) had an important influence on the changes in the unique phenolic profile of the sparkling wines elaborated with nontraditional varieties. PRACTICAL APPLICATION: In sparkling wines production, the secondary fermentation occurring in the sealed bottle during the vinification contributes greatly to their quality and sensory complexity. The Vitis labrusca and hybrid grapes varieties represent most of the grapes cultivated in Brazil being employed in the elaboration of juices and wines. These varieties present a great oenological potential and have not been explored yet regarding to the production of white sparkling wines. The use of these nontraditional grape varieties cultivated in South Brazil may be a viable alternative in the production of white sparkling wines with biological aging potential and particular bioactive properties.

Changes in organic acids, polyphenolic and elemental composition of rosé sparkling wines treated with mannoproteins during over-lees aging.

The effect of mannoproteins on the evolution of rosé sparkling wines during over-lees aging was investigated on the basis of the chemical characterization of polyphenols, organic acids, macro- and microelements using a combined analytical approach. Variations on these constituents were assessed using Raman and near-infrared spectroscopy. During the biological aging, caffeic acid, catechin, gallic acid and malvidin-3-O-glucoside were the most abundant polyphenolics in the rosé wines. The phenolic compound tyrosol, a fermentation derivative, was found at concentrations up to 98.07 mg L-1. The addition of mannoproteins significantly affected the concentrations of organic acids and individual polyphenolic compounds, particularly trans-resveratrol, quercetin, catechin, p-coumaric and hydroxybenzoic acids that showed increased concentrations over time. The positive effects of mannoproteins were mainly observed at the end of the biological aging. The mineral composition remained stable, while potassium was the most abundant mineral in all wines. The observed changes involving these constituents may offer new insights on their behavior during wine aging and on the bioactive and nutritional quality of rosé sparkling wines.

Rosé Sparkling Wines: Influence of Winemaking Practices on the Phytochemical Polyphenol During Aging on Lees and Commercial Storage.

The effects of oenological agents, gum arabic, and oenological tannin, added at two different stages in the winemaking of rosé sparkling wines (addition to the base wine and to the sparkling wine after disgorging) on evolution of the phytochemical composition during aging on lees and commercial storage were studied for the first time. The sparkling wines were monitored during 12 months of aging on lees (sur lie, with lees) and commercial storage (bottle storage, without lees), in terms of the polyphenolics, color intensity and antioxidant capacity. It was observed that the stage of the addition of oenological agents influenced the changes in phytochemical polyphenols and antioxidant capacity of sparkling wines. The most notable effects on the polyphenolics were observed in the experiment with the addition of oenological agents to the base wine, which significantly increased the concentrations of trans-resveratrol, gallic and ellagic acids, catechin, quercetin, and myricetin. The addition of oenological agents after the disgorging stage had less influence on the phenolics of the sparkling wines. Caffeic acid, trans-caftaric acid, catechin, tyrosol, and gallic acid were the most abundant polyphenolics in rosé sparkling wines. The winemaking practices evaluated in this study comprise an interesting approach to the improvement and/or maintenance of the polyphenolics, according to winemaking practices, besides providing new knowledge on the evolution of rosé sparkling wines. PRACTICAL APPLICATIONS: Tannins and gum arabic are been described as oenological agents, however, are poorly explored in rosé sparkling wines. Many chemical modifications that occur during the winemaking process, especially due to the second in-bottle fermentation and the yeast contact in the case of sparkling wines, can be determinant of authenticity and quality of sparkling wines. The addition of oenological agents in different stages of the winemaking can provide new insights into the evolution of phytochemical constituents of rosé sparkling wines and draw perspectives for improving technological properties of these wines based on practical experience.