Antonio De Gianni

Effects of defoliation on quality attributes of Nero di Troia (Vitis vinifera L.) grape and wine

Field studies were conducted in Puglia (Italy) to evaluate the influence of defoliation around cluster zones on grape and wine quality. Nero di Troia grapes were subjected to four different treatments: N: no leaf removal; E: leaf removal in the area of the clusters along the east side (at complete veraison); E/W: leaf removal in the area of the clusters along the east and west side (at complete veraison); and F: almost complete leaf removal along the west side (at complete veraison) and at pre-harvest also along the east side. Grapes of defoliated vines generally showed higher sugar content, lower titratable acidity, total flavonoids, flavonoids different from anthocyanins, and total phenolic content than grapes from non-defoliated vines while their total anthocyanin concentration was not affected by defoliation at a significant level. Concerning wines, alcohol content, residual soluble solids, different forms of anthocyanins but also volatile acidity were generally higher in samples from defoliated vines. Differences were also highlighted among the defoliation treatments: the best results in terms of dry matter, sugar and alcohol content were observed in the samples submitted to the more severe defoliation as a consequence of the higher light availability and berry temperature. Concerning the concentration of the individual phenolics, significant differences were highlighted for: caffeic and caftaric acids, peonidin- and malvidin-3-p-coumaroylglucoside, which were higher in the E wines; quercetin-3-glucoside, galactoside, and rhamnoside, and procyanidins, which were higher in F wines.

Differential Adsorption of Ochratoxin A and Anthocyanins by Inactivated Yeasts and Yeast Cell Walls during Simulation of Wine Aging.

The adsorption of ochratoxin A (OTA) by yeasts is a promising approach for the decontamination of musts and wines, but some potential competitive or interactive phenomena between mycotoxin, yeast cells, and anthocyanins might modify the intensity of the phenomenon. The aim of this study was to examine OTA adsorption by two strains of Saccharomyces cerevisiae (the wild strain W13, and the commercial isolate BM45), previously inactivated by heat, and a yeast cell wall preparation. Experiments were conducted using Nero di Troia red wine contaminated with 2 μg/L OTA and supplemented with yeast biomass (20 g/L). The samples were analyzed periodically to assess mycotoxin concentration, chromatic characteristics, and total anthocyanins over 84 days of aging. Yeast cell walls revealed the highest OTA-adsorption in comparison to thermally-inactivated cells (50% vs. 43% toxin reduction), whilst no significant differences were found for the amount of adsorbed anthocyanins in OTA-contaminated and control wines. OTA and anthocyanins adsorption were not competitive phenomena. Unfortunately, the addition of yeast cells to wine could cause color loss; therefore, yeast selection should also focus on this trait to select the best strain.

The effect of in-amphorae aging on oenological parameters, phenolic profile and volatile composition of Minutolo white wine

A wine was obtained from cryomacerated Minutolo grapes under reductive conditions and aged for 12months in glass container and in 3 types of amphorae. After aging, wines in glass containers showed the highest alcohol content, volatile acidity, dissolved oxygen, concentrations of aromatics, alcohols, and esters and by the lowest contents of enols and terpenes. They also showed the highest decrease of flavonoids, hydroxycinnamoyl tartaric acids, and procyanidins. Wines in raw amphorae showed the dramatic decrease of flavonoids and flavans reactive with vanillin. The highest antioxidant activity was exhibited by wines in engobe amphorae, while the lowest values were showed by the wines in glass containers and glazed amphorae. Caftaric acid and procyanidin B3 decreased in wine aged under glass while epicatechin mainly reduced in raw amphorae. According to the Principal Component Analysis, the wines resulted homogeneously grouped as a function of the type of container in which were aged.

A study on the effects of oxygen transmission rate of synthetic stopper on wine quality: the case of Nero di Troia

The aim of this work was to study the effect of closure oxygen permeability (OTR) on chemical, physical, and sensory qualities of Nero di Troia wines. The wines were produced, bottled, and closed with three types of coextruded synthetic stoppers differing for their OTR (low, medium, and high). The wines of the bottles closed with high OTR stoppers exhibited the lowest concentrations of all the phenolic classes, except for monomeric anthocyanins. The oxygen permeating through the medium and high OTR stoppers favored the increases in polymerization reactions within tannins and between flavan-3-ols and anthocyanins. Color intensity showed the lowest values in wines sealed with low OTR closures. The wines of bottle with medium or high OTR closures had the highest monomeric-to-more stable pigments ratio. The wines stored in bottles sealed with low OTR closures showed a flavor profile characterized by vinous, floral, fruity, and ethereal notes, while those of bottles closed with medium and high OTR stoppers showed high fruity, spicy, and aromatic flavors. The types of closure exert significant effects on Nero di Troia wine quality in particular on color, which was stabilized by polymerization between anthocyanins and flavanols.