The natural method of winemaking is the result of a series of biochemical transformations caused by the action of several enzymes. Many of these enzymes originate from the grapes themselves. However, the enzymes found in the grapes, yeasts and other microorganisms are often not sufficient so commercial enzymes are often added to supplement winemaking requirements.

Enzymes are used in winemaking to break down certain components in the grape juice, such as pectin and proteins, which help clarify the wine and improve its flavour, as well as improve the quality and efficiency of the fermentation process. Enzymes are also used to remove unwanted substances such as tannins.

To accomplish all this several different types of enzymes are used.

Pectinases are enzymes that break down pectin, which is a complex carbohydrate found in the cell walls of the plants.  The result is simpler sugars that can be fermented by yeast.

Beta-glucanases break down beta-glucans, which are complex sugars found in the cell walls of yeast and can cause problems during fermentation.

Proteases are enzymes that break down proteins into smaller peptides and amino acids, which can also be utilized by yeast during fermentation.

Glucosidases help to release aromatic compounds from the grape juice, which can enhance the flavour and aroma of the wine.  The selection of active yeast, fungal and bacterial glycosidases enhance the wine aroma.

Lipases are enzymes that break down fats and lipids, which can improve the clarity, filtration and stability of the wine.  They also assist with improving the pressing efficiency and juice extraction.

Anthocyanins contribute greatly to red wines because these molecules and their interactions with other compounds are responsible for the colour and the stability of red wine during ageing.

Exogenous enzymes are often used to accelerate the extraction of anthocyanins from the berry skin increasing the colour intensity of the wine.

The diagram below demonstrates where enzymes may be injected into the wine making process.  It is an excellent illustration as to why vintners require a strong biology or bio-chemical background.

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