Tomás Román Villegas

Arsenic present in the soil‐vine‐wine chain in vineyards situated in an old mining area in Trentino, Italy

The present study follows arsenic (As) transfer through the chain of soil-vine-leaves-grapes-wine to assess the possible risk of arsenic intake related to consuming grapes and wines produced in 10 vineyards located in a mining area rich in this element. The results are compared with date from 18 uncontaminated areas. In the soil, the content of As extracted with acqua regia and that extracted with ammonium acetate, were analyzed. Leaves and berries were analyzed after washing with acidified aqueous solution and acid mineralization in a closed vessel, whereas wines were simply diluted before analysis. All analyses were performed using an inductively coupled plasma mass-spectrometer. The aqua regia extractable As concentration in soil ranged from 3.7 to 283 mg/kg, whereas available As varied from 18 to 639 µg/kg, and As total concentration ranged from 16.3 to 579 µg/kg dry weight in leaves and from <0.1 to 36.8 µg/kg dry weight in grapes. Arsenic levels in wines were always below 1.62 µg/L, with higher concentration in red wines than in white wines. Significant and positive correlations between the As concentrations in soils, leaves, and berries are highlighted, with the samples collected near the mining area having significantly higher values. Nevertheless, As levels in wines were always well below the limit (200 µg/L) suggested by the International Organization of Vine and Wine.

Novel technological strategies to enhance tropical thiol precursors in winemaking by-products

Grape pomace is a winemaking by-product that can be used to extract oenological tannins. Recently, some grape skin tannins were shown to contain very high amounts of two polyfunctional thiol precursors (3-S-glutathionylhexan-1-ol, 3-S-cysteinylhexan-1-ol) whose free forms are responsible for appreciated tropical-like flavours. This study shows that an oxidative treatment (no SO2) of white grape pomace and the presence of grape leaves and stems can increase the content of the above mentioned precursors. Moreover, it shows significant differences between Sauvignon Blanc, Gewuerztraminer and Mueller-Thurgau grape pomace for the 3-mercaptohexan-1-ol precursors and 4-S-cysteinyl-4-methylpentan-2-one. The grape cultivar is crucial, but the technological ability of enhancing the level of the volatile thiol precursors simply by treating the grape marc in different ways is a promising and powerful tool for the production of potentially flavouring tannins intended for food and beverage industry.

Rapid Analysis of 27 Volatile Sulfur Compounds in Wine by Headspace Solid-Phase Microextraction Gas Chromatography Tandem Mass Spectrometry

Volatile sulfur-containing compounds (VSCs) play an important role in wine aroma conferring at high concentrations unpleasant odors but also participating positively at low concentration. A large number of VSCs are formed at different stages of winemaking and storage. To monitor this phenomenon, a HS-SPME-GC-MS/MS method has been developed. The method is proposed in order to quantify 27 different sulfur-containing compounds. SPME extraction was performed using a carboxen-polydimethylsiloxane (CAR-PDMS) fiber, which resulted the most effective fiber coating. Time and temperature extraction conditions were optimized using response surface methodology. The selectivity and sensitivity of the method were considerably increased using triple-quadrupole in multiple reaction monitoring (MRM) mode. The number of VSCs analyzed in a single run was higher than in any other method previously reported using single-quadrupole MS or other detectors. The overall process was successfully applied to identify and quantify sulfur compounds both in white and red wines.

Exploitation of simultaneous alcoholic and malolactic fermentation of Incrocio Manzoni, a traditional Italian white wine

Malolactic fermentation (MLF) is a key feature in the production of high-quality wines. Its evolution is not always guaranteed, especially in white wine, due to certain limiting factors (low pH, sulphur dioxide, low temperature) acting against malolactic bacteria. The inoculation of grape must with bacteria is an alternative approach to the management of oenological fermentation, favouring the survival of bacteria due to the absence of ethanol or sulphur dioxide – toxic compounds made by yeasts in the first stages of winemaking. We compared the activity of two strains of Oenococcus oeni during MLF in wines made from an emerging white grape variety, native to north-eastern Italy, namely Incrocio Manzoni. Different winemaking protocols were assayed, comparing sequential or simultaneous inoculation of microbial starters. The monitoring of bacterial viability through fermentations and a comprehensive characterisation of the volatile profile of the wines were achieved by advanced analytical approaches, flow cytometry and GC-MS respectively. According to the preliminary hypothesis, the chemical composition of the grape must was characterised by high acidity, which represented a serious barrier to bacterial development. Simultaneous inoculation of the two O. oeni strains ensured a regular evolution of MLF. Some differences were highlighted, both in terms of fermentation kinetics and the aromatic profile of the wines obtained, in relation to the strain of lactic bacteria. The work provides an exhaustive overview of the opportunities and risks related to different wine fermentation approaches in order to enhance the quality of white wines made from “new” or “local” wine grapes.

Targeted and untargeted high resolution mass approach for a putative profiling of glycosylated simple phenols in hybrid grapes

Vitis vinifera is one of the most widespread grapevines around the world representing the raw material for high quality wine production. The availability of more resistant interspecific hybrid vine varieties, developed from crosses between Vitis vinifera and other Vitis species, has generated much interest, also due to the low environmental effect of production. However, hybrid grape wine composition and varietal differences between interspecific hybrids have not been well defined, particularly for the simple phenols profile. The dynamic of these phenols in wines, where the glycosylated forms can be transformed into the free ones during winemaking, also raises an increasing health interest by their role as antoxidants in wine consumers. In this work an on-line SPE clean-up device, to reduce matrix interference, was combined with ultra-high liquid chromatography-high resolution mass spectrometry in order to increase understanding of the phenolic composition of hybrid grape varieties. Specifically, the phenolic composition of 4 hybrid grape varieties (red, Cabernet Cantor and Prior; white, Muscaris and Solaris) and 2 European grape varieties (red, Merlot; white, Chardonnay) was investigated, focusing on free and glycosidically bound simple phenols and considering compound distribution in pulp, skin, seeds and wine. Using a targeted approach 53 free simple phenols and 7 glycosidic precursors were quantified with quantification limits ranging from 0.001 to 2mgKg-1 and calibration R2 of 0.99 for over 86% of compounds. The untargeted approach made it possible to tentatively identify 79 glycosylated precursors of selected free simple phenols in the form of -hexoside (N=30), -pentoside (21), -hexoside-hexoside (17), -hexoside-pentoside (4), -pentoside-hexoside (5) and -pentoside-pentoside (2) derivatives on the basis of accurate mass, isotopic pattern and MS/MS fragmentation.