Enzymes and Winemaking
Application of Enzymes in Wine Production
Enzymes can be used at several stages in winemaking. These uses tend to fall into just a few categories: juice extraction, clarification, aging on lees, aroma enhancement post-fermentation, and filtration. Enzymes are sold as direct-addition powders and few are sold as live enzymes in liquid solution. In all cases, follow the manufacturer's instructions carefully as the concentration and activity can vary substantially with recommended rates. It is important to note that there can be significant differences between results obtained with different suppliers' enzymes.
Juice Extraction
The pulp of the grape varieties is rich in pectin compounds (e.g., Muscat, Sylvaner, etc.). Pectin is a polysaccharide starch found in the cell walls of grapes. The incomplete hydrolysis of these molecules by the endogenous enzymes can therefore cause problems in processing. If pectinases are applied to the pulp prior to pressing, they can improve juice and color yield.
White or Rose Winemaking
For white or rose winemaking, enzymes can be used for two reasons. The first is to increase both the quantity of good quality free-run juice, as well as the overall quantity of juice per ton of grapes crushed.
Red Winemaking
Besides increasing the yield, there are numerous advantages associated with the use of macerating enzymes in red winemaking. For example, pectinases greatly facilitate color and tannin extraction, since anthocyanins and tannins are located in the skins of red grapes.
Clarification
Settling or flotation is a very important process in white and rose winemaking as it enhances the aromatic finesse of wines. In red wines, it is also useful to finish alcoholic fermentation or to start malolactic fermentation with clean wines and is essential to young red wine quality produced by thermovinification. Grape macromolecules such as polysaccharides affect the colloidal make-up of wine by keeping grape solid particles in suspension. Degradation of pectins with pectinases will greatly diminish the colloidal load and lead to agglomeration of the particles.
Aging on Lees
The practice of wines after fermentation on either the gross or fine lees is very common (Section 8.5). One of the major mechanisms involved during this process is the yeast autolysis liberating intracellular substances such as nitrogenous compounds (e.g., amino acids and peptides) as well as polysaccharide breakdown products, such as mannoproteins. All these compounds have a direct or indirect positive influence on wine quality.
Aroma Release Post-Fermentation
Glycosidase enzymes are used to unbind aroma compounds, thereby greatly enhancing the aromatic potential of wines. Wines that benefit from this treatment are those made from monoterpene containing grape varieties, such as Riesling, Gewurztraminer, all the Muscat varieties, and certain neutral varieties to some extent.
Filtration
Botrytis and Saccharomyces secrete long chain glucans into grape juice and wine, resulting in poor filterability that can also be worsened by the presence of residual pectins.
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