Francesca Sonni

Antioxidant action of glutathione and the ascorbic acid/glutathione pair in a model white wine

Glutathione was assessed individually, and in combination with ascorbic acid, for its ability to act as an antioxidant with respect to color development in an oxidizing model white wine system. Glutathione was utilized at concentrations normally found in wine (30 mg/L), as well as at concentrations 20-fold higher (860 mg/L), the latter to afford ascorbic acid (500 mg/L) to glutathione ratios of 1:1. The model wine systems were stored at 45 °C without sulfur dioxide and at saturated oxygen levels, thereby in conditions highly conducive to oxidation. Under these conditions the results demonstrated the higher concentration of glutathione could initially provide protection against oxidative coloration, but eventually induced color formation. In the period during which glutathione offered a protective effect, the production of xanthylium cation pigment precursors and o-quinone-derived phenolic compounds was limited. When glutathione induced coloration, polymeric pigments were formed, but these were different from those found in model wine solutions without glutathione. In the presence of ascorbic acid, high concentrations of glutathione were able to delay the decay in ascorbic acid and inhibit the reaction of ascorbic acid degradation products with the wine flavanol compound (+)-catechin. However, on depletion, the glutathione again induced the production of a range of different polymeric pigments. These results highlight new mechanisms through which glutathione can offer both protection and spoilage during the oxidative coloration of a model wine.

Gas chromatography-mass spectrometry (GC-MS) characterization of volatile compounds in quality vinegars with protected european geographical indication.

The volatile composition of 26 premium quality vinegars belonging to three different protected geographical indications (traditional balsamic vinegar of Modena, balsamic vinegar of Modena, and sherry vinegar) has been characterized by means of a solid-phase extraction (SPE) gas chromatography-mass spectrometry GC-MS method. Among the about 90 quantified compounds, short-chain fatty acids, furanic compounds, enolic derivatives, and some esters were found to discriminate the samples as a consequence of differences in the extent of Maillard reactions, presence of alcoholic fermentation, or duration of wood aging.

Impact of Glutathione on the Formation of Methylmethine- and Carboxymethine-Bridged (+)-Catechin Dimers in a Model Wine System

This study was performed to assess the impact of glutathione on the reaction between (+)-catechin and carbonyl compounds in wine-related conditions. (+)-Catechin (0.50 mM) and either glyoxylic acid (0.25 mM) or acetaldehyde (0.25 mM) were added to a model wine system with 0.0, 0.25, and 2.5 mM of glutathione added. UPLC-DAD and LC-MS analysis showed that the formation of carbonyl-bridged (+)-catechin dimers was inhibited in the samples with a glutathione to carbonyl ratio of 10:1 compared to the samples without glutathione. At a ratio of 1:1, glutathione inhibited the acetaldehyde-bridged dimers but only had a minor impact on the glyoxylic acid-bridged dimers. Further investigations showed that this trend of inhibition by glutathione on the glyoxylic acid-derived dimer was independent of temperatures, 20 °C vs 45 °C, or the presence of metal ions, 0.2 mg/L copper(II) and 5 mg/L iron(II). (1)H NMR analysis and LC-MS analysis provided evidence that glutathione inhibited dimer formation via different mechanisms depending on the carbonyl compound. For acetaldehyde-derived dimers, the main mode of inhibition was the ability of glutathione to form a (methyl-glutathionyl-methine)-(+)-catechin complex. Alternatively, the formation of a glutathione-glyoxylic acid addition product impeded the reaction between glyoxylic acid with (+)-catechin. These results demonstrate that glutathione, at sufficient concentration, can have a substantial impact on carbonyl-derived polymerization reactions in wine-like conditions.

Pre-fermentative replacement of sulphur dioxide by lysozyme and oenological tannins: Effect on the formation and evolution of volatile compounds during the bottle storage of white wines

In this work, the effects on the volatile profile of the pre-fermentative substitution of SO2 with lysozyme and oenological tannins were studied in white wines. At the same time, in order to understand the changes of volatile compounds in SO2-free wines, the evolution of volatiles was evaluated over 1year of storage in bottles. For this purpose, a number of laboratory scale fermentations of SauvignonBlanc musts were carried out and the effects of three variables (SO2, lysozyme and oenological tannins) were investigated by means of GC-MS analysis. Results showed that the replacement of SO2 with lysozyme and oenological tannins influenced the volatile composition of wines at the end of the alcoholic fermentation. Wines fermented with SO2 showed higher total alcohol amounts, while the presence of oenological tannins augmented the level of esters. The presence of SO2 influenced also the alcohols and esters profiles of wines during bottle storage. Moreover, the presence of oenological tannins displayed a positive role in maintaining the amounts of esters over certain levels in wine stored for 1year, likely due to their oxygen scavenging ability. By contrast, acids were less affected by the investigated adjuvants both at the end of the alcoholic fermentation and during the storage time.

Comparative Changes in Color Features and Pigment Composition of Red Wines Aged in Oak and Cherry Wood Casks

The color features and the evolution of both the monomeric and the derived pigments of red wines aged in oak and cherry 225 L barriques have been investigated during a four months period. For cherry wood, the utilization of 1000 L casks was tested as well. The use of cherry casks resulted in a faster evolution of pigments with a rapid decline of monomeric anthocyanins and a quick augmentation formation of derived and polymeric compounds. At the end of the aging, wines stored in oak and cherry barriques lost, respectively, about 20% and 80% of the initial pigment amount, while in the 1000 L cherry casks, the same compounds diminished by about 60%. Ethyl-bridged adducts and vitisins were the main class of derivatives formed, representing up to 25% of the total pigment amount in the cherry aged samples. Color density augmented in both the oak and cherry wood aged samples, but the latter had the highest values of this parameter. Because of the highly oxidative behavior of the cherry barriques, the use of larger casks (e.g., 1000 L) is proposed in the case of prolonged aging times.