Vatting times

In Eq. (5.2.15) it is very important to bear in mind that the sum is only over those molecules which are in the illuminated volume Vat times zero and t. In order to make this fact explicit we define a quantity having the following properties... 

Table 12.1. Influence of different parts of the grape cluster on phenolic compounds and wine color (Malbec, fermentation at 25°C, vatting time 10 days) (Rib6reau-Gayon et al, 1976)...

Evidently, these notions pertaining to the evolution of color and anthocyanins in terms of maceration time primarily concern new wines—anthocyanins are in fact the essential elements of their color. As wine matures, the role of tannins becomes increasingly important. Extended vatting times produce more colored wines, even if the resulting new wines initially appear to confirm the contrary. 

Generally speaking, according to Boulet and Escudier (1998), wines treated by Flash-detente contain 30-60% more polyphenols than controls, even after the traditional 3-week vatting time on the skins. 

Choosing the optimal vatting time is a complicated decision with many possible solutions. It depends on the type of wine desired, the characteristics preferred (tannin intensity and harmonious structure are not always compatible) and the nature of the grape. This decision also depends on... 

Table 12.10. Alcohol loss according to vatting time in an open tank (Ferr6, 1958)...

Vatting time (days) Density at devatting Temperature at devatting (°C) Alcoholic strength of wine (% vol.) Alcohol loss (% vol.)... 

In fact, vatting times do not follow precise rules. They depend on the kind of wine desired and on grape quality. 

First of all, the various forms of rot impart mushroom-like, iodine-like and moldy odors to wine. A short vatting time avoids their concentration. 

If the results of these tests are positive, an extended maceration is not necessary. A prolonged vatting time would in fact intensify the flaws due to grape rot. In this case, the wine should also be sulfited at the time of running-off the wine. Malolactic fermentation will of course be more difficult, but all oxidative risks are avoided during draining. 

The decision to blend press wines with free-run wines is complicated. It not only depends on both free-run and press wine quality but also on the type of wine desired. In general, press wines are not added when making primeur-style wines for early drinking, except when the press wines are excessively light. Moreover, press wines should not be incorporated into wines made from ordinary and rustic varieties. Premium wines made from very concentrated grapes are often very tannic, even after short vatting times the addition of press wines does not improve their overall quality. When possible, press wines that are not used for blending should be distilled. 

The following factors participate in the control of malolactic fermentation acidity (Section 6.2.1), temperature (Section 6.2.4), aeration (Section 6.2.5), vatting time and sulfiting (Section 6.2.2). 

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