Chapter 20

Enzymes and Winemaking

Role of Commercial Enzymes in Wine Production

Commercial enzymes are now accepted by many as an integral part of winemaking. With many suppliers offering a vast array of enzymes under different brand names, the choice available to winemakers is staggering. Current commercial enzyme preparations are usually cocktails of different activities, such as glucosidases, glucanases, and pectinases. To further confuse the matter, enzymes are usually defined by their activity rather than their exact chemical structures or even the biological source from which they are derived. A good understanding of enzymes and their specific role in winemaking applications is necessary to make informed decisions.

Pectinases

The enzymes responsible for breaking down pectin are collectively called pectinases. Pectinases liberated from the grapes themselves, however, are not very active under winemaking conditions. Commercial pectinasebased enzyme preparations work by cutting the long chains of pectins into smaller lengths (Section 1.1). The smaller the molecule, the less viscous it is.

Glucanases

White wines produced from botrytized grapes often present serious problems in clarification and filtration. The origin of this problem is usually long chain glucan molecules (i.e., ?-glucans), a polymer of glucose synthesized by Botrytis cinerea (Section 1.1).

Glycosidases

Grapes contain endogenous glycosidases, which are capable of slowly releasing the volatile flavor components from their non-aromatic precursors, but under wine making conditions, they are not very efficient because they work more effectively around a pH of 5.

Cellulases and Hemicellulases

Cellulase breaks down cellulose to either simple glucose or into glucose-disaccharide. Cellulose is a polysaccharide of glucose. Hemicellulase breaks down hemicellulose. Hemicelluloses are polysaccharides composed of a broad range of simple sugar monomers including glucose, xylose, arabinose, galactose, mannose, and rhamnose.

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