Wine color

Some structural changes of the native flavonoids occur during wine conservation, and one of the most studied of those changes concerns red wine color evolution, called wine aging. It has been demonstrated that as a wine ages, the initially present grape pigments slowly turn into new, more stable red pig-... 

In severe cases, dark port-wine color to urine on standing... 

Mercury(II) sulfate is an electrolyte for primary batteries. Other apphca-tions are in extraction of gold and silver from roasted pyrites as a catalyst in organic reactions such as conversion of acetylene to acetaldehyde and as a reagent for wine coloring. 

Pectinases and (3-glucanases are the only enzymes allowed in wine-making by European legislation. They are used as clarification and filtration agents and also to release aroma compounds that are mostly present in grape as nonvolatile glycosidic precursors. Pectolytic enzymes are also reported to increase extraction of phenolic compounds and wine color... 

Thus, the intense red wine color and its preservation over years require some pigment stabilizing mechanisms to take place. Such stabilization is achieved, on the one hand, through... 

Brouillard, R., Chassaing, S., and Fougerousse, A., Why are grape/fresh wine anthocyanins so simple and why is it that red wine color lasts so long Phytochemistry, 64, 1179, 2003. 

B. Influence of SO2 and wine antioxidants C. Effects on red wine color and polyphenol 162... 

The trends in wine pigment development seen above for the SO2 study have been consistently reported in MOX trials. These include a greater formation of sulfite-resistant pigments, a more rapid loss of monomeric anthocyanins, and a greater retention of wine color. Higher color intensity was one of the findings reported in early research work on the MOX... 

TABLE 4.1 Changes in wine color parameters for a Cabernet Sauvignon wine subject to MOX for 7 months at 5 mL/L/month data from Atanasova et at. (2002)... 

FIGURE 4.8 Development of wine color properties for wines undergoing MOX at 3 mg/L/month (M), versus control wines (C) with the fraction of color due to the polymeric fraction (PP), free anthocyanins (FA), and copigmentation (CP) reported. Reprinted with permission from du Toit et al. (2006a). Copyright 2006 South African Society for Viticulture and Enology. 

TABLE 4.2 Changes in selected wine color parameters for a Monastrell wine subject to MOX, initially at 5 mL/L/month (Tl) and 10 mL/L/month (T2), at the end of MOX and after 6 months in the bottle data from Cano-Lopez et al. (2006, 2007)... 

In further trials on Mencia and Tinta del Paris wines, the presence of French or American oak chips af 4 g/L during MOX led fo very few observable differences in terms of pol) henol and color parameters (Perez-Magarino et ah, 2009). Some influence of oak toasting degree was related to the ability of compounds released from fhe chips fo combine with anthocyanins to form new pigmenfs, and fo a differenf extent with the two wines examined, but these effects were outweighed by the impact of MOX itself on phenolic composifion and wine color. 

Laurie, V. F. and Waterhouse, A. L. (2006b). Oxidation of glycerol in the presence of hydrogen peroxide and iron in model solutions and wine. Potential effects on wine color. J. Agric. Food Ghent. 54, 4668-4673. 

A statement of the problems relative to red wine color should include a description of the compounds involved which belong to plant phenolics. These compounds include the anthocyanins of grapes and the tannins which are important in the color of wines, especially old wines. 

Finally, we try to develop a chemical interpretation for the color of red wine—i.e., the specific role of different substances and the changes they undergo which cause the evolution of wine color, especially during aging. 

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