Cristina Lasanta

The influence of ripeness grade on the composition of musts and wines from Vitis vinifera cv. Tempranillo grown in a warm climate

Fruit ripeness has an influence on the phenolic and aromatic composition of grapes and musts and, therefore, on the sensorial characteristics of the resulting wine. The aim of the work described here was to assess the influence of the harvest date on the analytical composition of the musts and wines from the Vitis vinifera cv. Tempranillo grape grown in a warm climate. A hydroalcoholic medium was employed to extract the musts and simulate a traditional maceration process. Phenolic compounds were analysed by colorimetric methods and aroma compounds by gas chromatography/mass-spectrometry. Furthermore, the wines were tested by a sensory panel. A good correlation was obtained between the parameters measured in the must and in the corresponding wine, as well as in the scores recorded in the sensory analysis. In summary, grape ripening was found to have a marked influence on the wine composition and it was possible to establish the key parameters that need to be measured in the must during ripening to identify the optimal harvest date to obtain the best quality wine.

The influence of cation exchange treatment on the final characteristics of red wines.

Ion exchange technology has been applied to adjust the pH of red wine and improve its tartaric and oxidative stability. Ion exchange appears to be a useful technique to achieve these objectives. Regarding the effect of ion exchange on organoleptic characteristics and the quality of the obtained wines, a slight decrease in both anthocyanin and tannin contents was observed along with a small drop in the aromatic content. However, the treated wines had lower hue and higher colour intensity and gave better punctuations in the sensory evaluation. These results confirm that ion exchange is an interesting technique for application in red winemaking.

Chemical modeling for pH prediction of acidified musts with gypsum and tartaric acid in warm regions

Winemaking of musts acidified with up to 3g/L of gypsum (CaSO4 2H2O) and tartaric acid, both individually and in combination, as well as a chemical modeling have been carried out to study the behaviour of these compounds as acidifiers. Prior to fermentation gypsum and tartaric acid reduce the pH by 0.12 and 0.17 pH units/g/L, respectively, but while gypsum does not increase the total acidity and reduces buffering power, tartaric acid shows the opposite behaviour. When these compounds were used in combination, the doses of tartaric acid necessary to reach a suitable pH were reduced. Calcium concentrations increase considerably in gypsum-acidified must, although they fell markedly after fermentation over time. Sulfate concentrations also increased, although with doses of 2g/L they were lower than the maximum permitted level (2.5g/L). Chemical modeling gave good results and the errors in pH predictions were less than 5% in almost all cases.

Applications of Ion Exchangers in Alcohol Beverage Industry

There are numerous applications of ion exchange process in the alcohol beverage industry. Among the most widely used techniques are, on the one hand, the use of cation exchange in acid cycle to remove potassium and stabilize wine against the sediments of potassium bitartrate crystals and, on the other hand, a mixed anion and cation-exchange treatment of wine for cation and anion removal from grape must in grape sugar production. Today, only the two aforementioned ion exchange techniques are authorized by the European Union legislation. Unlike laws in the EU, the legislation in the member countries of the World Wine Trade Group (WWTG) is less restrictive and allows the use of ion exchange in other applications. In this way, cation exchange in acid cycle is used for must/wine acidification and chelating resins for the metal removal from wine. Last but not the least, anion-exchange resins are also employed for vinegar decolourization, protein content and volatile acidity reduction, and extraction of wine compounds of commercial interest. Ion exchange treatment is a cost-effective selective process in the alcohol beverage industry, thus becoming a very attractive option nowadays.