Use of computational modelling for selecting adsorbents for improved fining of wine

For characterization, sensory designing and authentication rapid analytical technologies have become available. Some, like Proton Transfer Reaction Mass Spectrometry allow a rapid spectrum of the volatile compounds of wines. Combined with chemometrics wines can be characterized. The same approach can be used to calculate the results of virtual mixtures and allow formulation of constant quality blends. Other new techniques and portable devices based on spectroscopy allow measurements on production sites and in grocery stores, even for the smart consumer. We will present some examples of the application of these techniques for authentication of wines, both in the laboratory and on site.

The production of red sparkling wines is lower in Spain in comparison with the winemaking of white or rosé sparkling wines. In red sparkling wine processing it is essential to obtain suitable base wines that should have moderate alcohol content, high acidity, good color values, an adequate mouth-feel and a sweet tannin. Grapes for sparkling wine production have to be harvested at low maturity stages, with lower alcohol contents and higher acidities, which will that the phenolic maturity of the grapes is also low, showing green tannins. This paper analyses different treatments in order to minimize these inconveniences: cold maceration-prefermentation and delestage to elaborate the grapes with lower maturity, must nanofiltration, and the partial osmosis of the wines made from grapes with an adequate maturity degree.

Varietal Riesling aroma relies strongly on the formation and liberation of bound aroma compounds. Floral monoterpenes, green C6-alcohols, fruity C13-norisoprenoids and spicy volatile phenols are predominantly bound to disaccharides, which are produced and stored in the grape berry during berry maturation. Grape processing aims to extract maximum amount of the precursors from the berry skin to increase the potential for a strong varietal aroma in the wine. Subsequent yeast selection plays an important part in this process.

Ellagitannin, anthocyanin and woody volatile composition of Cabernet Sauvignon wines aged in oak barrels for 12 months was evaluated. Depending on the container where malolactic fermentation (MLF) was carried out, two wine modalities were investigated: wines with MLF carried out in stainless steel tanks and barrel-fermented wines. Three toasting methods (medium toast, MT; medium toast with watering, MTAA; noisette) were considered for ageing of each wine modality. Sensory analyses (triangle and rating tests) were also performed. Two-way ANOVA of the raw experimental data revealed that the toasting method and the container where MLF took place, as well as the interaction between both factors, have a significant influence (p < 0.05) on ellagitannin, anthocyanin and woody volatile profiles of Cabernet Sauvignon wines.

A misconception lingers in the minds of some wine consumers that Champagne wines don’t age. It’s largely a myth, certainly as far as the best cuvees are concerned. Actually, during the so-called autolysis period of time (in the closed bottle, after the “prise de mousse”), complex chemical reactions take place when the wine remains in contact with the dead yeast cells, which progressively bring complex and very much sought-after aromas to champagne. Nevertheless, despite their remarkable impermeability to liquid and air, caps or natural cork stoppers used to cork the bottles are not 100% hermetic with regard to gas transfers. Gas species therefore very slowly diffuse through the cap or cork stopper, along their respective inverse partial pressure. After the “prise de mousse”, because the partial pressure of CO2 in the bottleneck reaches up to 6 bars (at 12 °C), gaseous CO2 progressively diffuse from the bottle to the ambient air
(where the partial pressure of gaseous CO2 is only of order of 0,0004 bar).