Tannins anthocyanins combined with

Anthocyanins (At) are present in wine in different forms free anthocyanins (Al) and anthocyanins combined with tannins (Ac), some of which are bleached by SO2 (TA), while the rest is unaffected (TAT) ... 

If the coloring matter in red wine consisted only of free anthocyanins (Al), given the usual pH (3.4-4.0) and free SO2 concentration (10-30 mg/1), the coloring percentages would be lower (3-14%). The new pigments produced when anthocyanins combine with tannins are much less... 

A more detailed analysis of Pontallier s experiment (1981) makes it possible to distinguish between the free anthocyanin concentration (Al) and that of anthocyanins combined with tannins (T-A) (Section 6.4.2). Multiplying each of these values by the ionization value (Section 6.4.5) indicates the proportion of each type of molecule in colored form. The difference represents the... 

Microoxygenation is a technique that involves the addition of small and controlled quantities of oxygen to the wine. This technique is mainly used to stabilize the colour of red wines, since oxygen in small quantities favours polymerization reactions among anthocyanins and tannins (Atanasova et al. 2002). Globally, total anthocyanins decrease, but what is formed, combined with tannins, leads to a product which is more intensely coloured and more stable over time than the initial compounds. 

NaCl. It was not possible to isolate anthocyanins and their combinations with tannins. 

Anthocyanins and their combinations with tannins are not very astringent, bnt have a marked bitterness, especially in yonng wines, i.e. when the molecular structures are well defined and not too complex. 

At the time of botthng, a large proportion of the anthocyanins (over 50%) is already combined with tannins, in the form of reddish-purple complexes with ethyl cross-bonds, formed during aging in an oxidizing medium (Section 6.3.10). During bottle aging, some of these complexes... 

As the pH is raised, more pseudobase is formed and the color becomes weaker. However, in addition to pH, other factors influence the color of anthocyanins, including metal chelation and combination with other flavonoids and tannins. 

Several products and plausible mechanisms have been described for the incorporation of anthocyanins into the tannin pool (11-13). Confirming the structure of these species is likely to be a formidable challenge due to the complexity of the likely products combined with limitations in the chromatographic and characterization sciences. Nevertheless progress continues to be made (14,15). 

The Hagerman and Butler method for tannin analysis was combined with bisulfite bleaching of monomeric anthocyanins to give estimates of polymeric... 

Finally, the reactive carbonium ion combines with an anthocyanin to produce a tannin-anthocyanin dimer. This scenario is similar to that occurring during normal wine aging. 

During aging, the tannins become softer as they polymerize or combine with anthocyanins, while coloring matter precipitates and the color changes. The less oxidized ruby ports maintain the fruitiness and robustness of young wines. They have a more or less dark red color. The older, more oxidized tawny ports are golden red or golden. 

Anthocyanin molecules are not very stable, so their concentration in wine drops sharply during the first few months of barrel aging. They disappear completely in a few years, although the wine remains red. This decrease is due to combination reactions with various other compounds in the wine, especially tannins, as well as breakdown reactions. 

SO2 can also bind with phenolic compounds. In the case of proanthocyanic tannins, a solution of 1 g/1 binds with 20 mg/I of SO2 per liter. The combinations are significant with anthocyanins. These reactions are directly visible by the decoloration produced. The combination is reversible the color reappears when the free sulfur dioxide disappears. This reaction is related to temperature (Section 8.5.2) and acidity (Section 8.5.1), which affect the quantity of free SO2. The SO2 involved in these combinations is probably titrated by iodine along with the free SO2. In fact, due to their low stability, they are progressively dissociated to reestablish the equilibrium as the free SO2 is oxidized by iodine. 

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