5 Use of Enological Additives for Colloid and Tartrate Salt Stabilization 147
5.1.7 Wine Fining: General Conclusion and Practical
Recommendations
Carefully controlled laboratory fining trials must be performed before any agent is
added to cellar wines. In evaluating fining trials, the winemaker must observe, note
and record how each fining agent alters clarity, lees production, lees compaction,
colloidal stability, color, body (front, middle,and finish), astringency, bitterness, the
nose characteristics in general, the fruit, the finish, the aging potential, and overall
wine palatability. To be able to duplicate laboratory trials in the cellar, the same
lot of fining agent must be prepared and used in the same manner. A final analysis
of protein stability should be performed just prior to bottling. Overall, winemakers
have to remember than any changes in the wine pH and/or phenolic composition
(oxidation) could modify protein stability.
5.2 Use of Adjuvants for Stabilizing Wine with Respect
to Tartrate Salt Crystallization
The major physical instability in bottled winesremains precipitation of the tartaric
salts, that is, potassium hydrogenotartrate (KHT) and calcium tartrate (TCa). Stabi-
lization of these in bottled wines is desirable as consumers find them objectionable
and an indication of poor quality control.The initial instability of KHT and TCa
is caused by supersaturated levels in musts that are increased by a diminution in
salt solubilities (due to the presence of ethanol) and the low temperatures used for
wine storage. Thus, stabilization of wine with respect to potassium hydrogen tartrate
and calcium tartrate crystallization is a critical point, especially in the winemak-
ing process in Champagne or sparkling wine production. Before being stabilized,
wines may be filtered on a simple continuous earth filter in order to remove macro-
molecules known as “protective colloids” which are able to inhibit crystallization
of tartrate salts. The stability usually required, for instance, in Champagne wines
corresponds to the temperature of− 4 ◦C. Briefly, potassium hydrogen tartrate sta-
bilization is obtained by treating the wine with artificial cold using different tech-
nologies, namely, slow cold stabilization without KHT crystal seedling, rapid cold
stabilization including KHT crystal seedling by the static contact process or by the
dynamic continuous process.
Work has been done to find whether the very expensive treatment of wines with
artificial cold could be advantageously replaced by the addition of inhibitors of the
crystallization process of tartrate salts such as metatartaric acid, yeast mannopro-
teins or carboxymethylcellulose (CMC). Such inhibitors indeed increase the width
of the supersaturation field of both KHT and TCa in the wine, thus delaying tar-
trate salt precipitation in the bottle. Metatartaric acid is currently the product most
widely used for this purpose, though its efficacy is low as this compound does not
remain stable over time. Yeast mannoproteins possess stabilizing properties, which
result in the spontaneous improvement of protein and tartaric salt stability, as can be