Characterisation of Colour Components and Polymeric Pigments of Commercial Red Wines by Using Selected UV-Vis Spectrophotometric Methods

The composition of the colour components of commercial red wines from Italy was analysed in terms of total colour,co-pigmentation, SO2-resistant pigments, small and large polymeric pigments, and tannins. A total of 128 wines,including Sangiovese, Cabernet Sauvignon, Nero d’Avola, Merlot, Marzemino, Negroamaro, Aglianico, Cannonauand Rossese di dolceacqua from five vintages (1999 to 2003) were analysed. The composition of the wines showedsignificant differences in terms of total colour and co-pigmentation. Total colour at 520 nm was highest inMarzemino (7.50±1.5 AU, absorbance units), and then in Aglianico (7.10±2.8 AU) and Cabernet Sauvignon(5.01±2.50 AU). The level of large and small polymeric pigments in Sangiovese wines showed a range from 0.05 to0.40 and 0.10 to 0.27 AU 520 nm respectively. The variation in the level of polymeric pigments is affected by anumber of factors, including vintage, grape composition, fermentation and storage conditions

The Oxygen Consumption Kinetics of Commercial Oenological Tannins in Model Wine Solution and Chianti Red Wine

One property of oenological tannins, oxygen reactivity, is commonly exploited in winemaking. The reactivity is mediated by the presence of catalysts (i.e., transition metals and sulfur dioxide) and protects wine against oxidation. This work compares the oxygen consumption rate (OCR) of four commercial oenological tannins (two procyanidins from grape skin and seed, an ellagitannin from oak wood and a gallotannin from gallnut) in a model wine solution and Chianti red wine. All samples were subjected to consecutive cycles of air saturation at 20\ub0C to increase the total level of oxygen provided. After each cycle, the oxygen level was measured by means of a non-invasive luminescent sensor glued to a transparent surface (sensor dots) until there was no further change in substrate reactivity. The OCR followed first-order kinetics, regardless of the tannin. As expected, the ellagitannin showed the fastest OCR, followed by the two from grape seeds and skins and finally the gallotannin. The total O2 consumption in the red wine was almost double that of the model solution, due to the oxidation of wine substrates. The measurement of OCR is helpful for setting up an advanced winemaking protocol that makes use of tannins to reduce the use of sulfur dioxide

Suitability of the cyclic voltammetry measurements and DPPH\u2022 spectrophotometric assay to determine the antioxidant capacity of food-grade oenological tannins

Twenty commercially available oenological tannins (including hydrolysable and condensed) were assessed for their antiradical/reducing activity, comparing two analytical approaches: The 2,2-diphenyl-1-picrylhydrazyl (DPPH\u2022) radical scavenging spectrophotometric assay and the cyclic voltammetry (CV) electrochemical method. Electrochemical measurements were performed over a 12200 mV\u2013500 mV scan range, and integrated anodic currents to 500 mV were used to build a calibration graph with (+)-catechin as a reference standard (linear range: From 0.0078 to 1 mM, R2 = 0.9887). The CV results were compared with the DPPH\u2022 assay (expressed as % of radical scavenged in time), showing high correlation due to the similarity of the chemical mechanisms underlying both methods involving polyphenolic compounds as reductants. Improved correlation was observed by increasing the incubation time with DPPH\u2022 to 24 h (R2 = 0.925), demonstrating that the spectrophotometric method requires a long-term incubation to complete the scavenging reaction when high-molecular weight tannins are involved; this constraint has been overcome by using instant CV measurements. We concluded that the CV represents a valid alternative to the DPPH\u2022 colorimetric assay, taking advantage of fast analysis and control on the experimental conditions and, because of these properties, it can assist the quality control along the supply chain

Chemical composition and sensory evaluation of wines produced with different Moscato varieties

Moscato grapes give very aromatic musts and wines, characterized by the presence of monoterpenoids. The Farroupilha region situated in the highlands of South Brazil, is responsible for 50% of Brazilian Moscato wines production, and obtained its Geographical Indication (GI) in 2015. Brazilian Moscato wines are produced with several varieties, mainly Moscato Branco, Moscato Bianco R2 and Moscato Giallo. The objective of this study was to characterize the aromatic profile of wines produced with the three varieties. Microvinifications were conducted with grapes collected in three vineyards located in Farroupilha. Volatile compounds were evaluated using gas chromatography, and sensory characteristics were determined by a panel of enologists using a specific descriptive chard. Moscato Giallo wines exhibited the highest concentrations of ethyl acetate, 2-phenylethanol, isoamyl acetate, linalool, and α-terpineol; Moscato R2 wines showed the highest concentrations of ethyl decanoate and nerol, while Moscato Branco wines, the most representative variety of Brazilian sparkling Moscato wines, exhibited the highest concentrations of ethanal and ethyl hexanoate, and intermediary concentrations of the other compounds. In sensory analysis, the three varieties exhibited pear, pitanga, rosemary, and citric fruits aromas, but in general, Moscato Giallo and Moscato R2 were more intense, while Moscato Branco showed the highest acidity

L'uva e i sentori varietali

La conoscenza dei meccanismi che influenzano la formazione dei composti aromatici e precursori nell'uva \ue8 una prerogativa essenziale per la produzione di vini di qualit\ue0. Nel capitolo vengono trattati argomenti riguardanti l'origine degli aromi e il loro contributo al profilo aromatico del vino

Micro-oxygenation of red wine: Chemistry and sensory aspects.

Micro-oxygenation (MOX) is the process of introducing a low amount of oxygen during initial aging of red wine in the attempt to control desirable changes in its sensory properties. Although MOX can enhance the structure and colour of wine due to the reaction of phenolic compounds to form more stable polymeric structures, the reduction of astringency is less certain. It is also claimed that MOX might reduce excessively herbaceous character and reductive aroma of wine. MOX was developed during the early 1990s and is usually applied to red wines stored in steel tanks as alternative to oak ageing. The oxygen level into the wine over the course of treatment is the critical point to control the oxidation reactions that take place. Thus, the success of the MOX relies on the ability to control the rate of oxygen dosage. The MOX process is not well understood yet and represents one of the major controversial application of modern winemaking. The importance of oxygen level on the chemical and sensory changes of red wines is the central topic of this chapter

Enologia sostenibile. I vini biologici e biodinamici

Si riscontra un crescente interesse verso vini prodotti con processi a basso impatto ambientale e attraverso l\u2019adozione di una gestione altamente sostenibile del vigneto, quali biologica e biodinamica

Characterisation of Colour Components and Polymeric Pigments of Commercial Red Wines by Using Selected UV-Vis Spectrophotometric Methods

The composition of the colour components of commercial red wines from Italy was analysed in terms of total colour, co-pigmentation, SO2-resistant pigments, small and large polymeric pigments, and tannins. A total of 128 wines, including Sangiovese, Cabernet Sauvignon, Nero d\u2019Avola, Merlot, Marzemino, Negroamaro, Aglianico, Cannonau and Rossese di dolceacqua from five vintages (1999 to 2003) were analysed. The composition of the wines showed significant differences in terms of total colour and co-pigmentation. Total colour at 520 nm was highest in Marzemino (7.50\ub11.5 AU, absorbance units), and then in Aglianico (7.10\ub12.8 AU) and Cabernet Sauvignon (5.01\ub12.50 AU). The level of large and small polymeric pigments in Sangiovese wines showed a range from 0.05 to 0.40 and 0.10 to 0.27 AU 520 nm respectively. The variation in the level of polymeric pigments is affected by a number of factors, including vintage, grape composition, fermentation and storage condition