Why use enzymes in winemaking?
Enzymes are commonly used in winemaking. However, unlike yeast where the impact on the juice or must is easily observed and measured, the impact of enzymes is not so obvious. This article spells out the major applications of enzymes in winemaking and highlights the benefits of using these useful products.
What are enzymes?
Enzymes are naturally - occurring proteins. Each particular enzyme has a specific structure. All living things produce their own enzymes to carry out particular chemical reactions as part of their biological systems. Enzymes are nature’s catalysts: they facilitate these reactions but are not themselves used up in the reactions. Temperature and pH are critical parameters that affect their performance.
How are they produced commercially?
Enzymes are complex and are only produced by living things; that is, they are not synthetic chemicals. Enzymes are, therefore, not actually produced; they are extracted after growing certain micro-organisms in a fermentation system. For example, Aspergillus niger is a fungus that is commonly grown in fermentation vessels to produce a number of different enzymes. The enzymes that are produced by the micro-organism are then extracted and purified. This enzyme fermentation process has been used for more than 100 years, with the system not changed greatly in that time. However, the tools that are used to monitor, purify and blend the final product have improved greatly.
Enzymes are widely used for commercial purposes and in many industries, such as winemaking, brewing, baking and juice manufacture.
How can enzymes be used in winemaking?
Enzymes are used to reduce the impact of certain types of biological materials that can cause problems for the winemaker.
The main application of enzyme-use in winemaking is to reduce the impact of the long chain compounds – pectins, found in the non-woody parts of many plants. Pectins are a polymer of polygalacturonic acid, made up of the D-galacturonic acid monomer units – an oxidised form of the sugar galactose. Pectins can form a gel when in liquids. When your grandmother (or you!) make jam, the setting of the jam into a semi-solid material is due to the pectins from the fruit forming a gel.
While this gelling or setting is useful in jam-making, it is not a desirable property of wine. By adding enzymes that perform the activity of breaking down pectins (i.e., pectolytic activity), this gelling propensity is removed. Pectinases work by ‘cutting’ the long chains of pectins into smaller lengths. The smaller the molecule, the less viscous it is. When a pectolytic enzyme is added, the pectin molecules are reduced in size and better clarification can be achieved.
Another group of long chain molecules are the glucans. Glucans are a polysaccharide with the polymeric chains based upon the D-glucose monomer. Glucans are not normally found in healthy grapes. However, the mould Botrytis cinerea produces glucans when it infects grapes and other fruits. Although glucans have a different structure to pectins, they share some similar properties: they increase the viscosity of the wine and make it harder to process – particularly the filtering of the wine.
By adding an enzyme with glucanase activity, the glucans are also ‘cut’ in length and so filtration is much more easily achieved. The impacts on filtration are that the process is able to be achieved more quickly and less filtration media is needed.
A number of small compounds occur in wines that are bound to glucose molecules in the wine. These are known as glycosides. These glycosides can contain molecules called terpenes that will give off aromas if they are not bound to a glucose molecule.
By adding enzymes that have the ability to break these glycoside bonds (such enzymes have a glycosidase activity), the terpene compounds can be released and so a greater aroma profile can be achieved in the wine. Linalool, geraniol and citronellol are well-known terpenes.
The so-called aromatic varieties, such as Riesling and Gewürzt raminer, are well-known for containing terpenes and give good examples of typical terpene aromas.
What factors affect enzyme use?
Enzymes occur naturally in biological systems, so it is no surprise that the parameters affecting enzymes are similar to other living processes.
One key parameter is temperature: the lower the temperature, the lower the activity of an enzyme. At very high temperatures the protein structure of an enzyme is ruptured and so the enzyme is destroyed or denatured. To get the best use of an enzyme, the correct temperature range must be used. This is typically from 10-30°C.
Time is the other key variable in the effective use of enzymes. The longer an enzyme is left to do its work, the more work it can do. Of course, in the hectic pace of winemaking during vintage, there is often little time to leave enzymes to work. The difference between 30 minutes and one hour can be the extra time needed to make a difference in the impact of a pectolytic enzyme.
The other main parameter is dose rate. Commercial preparations of enzymes will have recommendations of the general dosage rate to use. This will usually be a range of dosages, as is will depend upon a number of factors such as grape variety, process used, temperature and time. To get the most out of the enzyme that you use, it is wise to work closely with your supplier to determine the most effective dosage rate, temperature and time of use.
Commercial enzymes from an experienced supplier are not usually the simple product of just one activity. For example, the product in question may have a main pectolytic activity but a secondary glucosidase or glucanase activity. Product specification sheets should spell out how the enzyme should be used and what impacts the enzyme preparation should achieve in your wine.
View our range of Winemaking Enzymes
Enzymes have an important role in modern winemaking. Having an understanding of the particular activities of an enzyme preparation, and taking care in ensuring the correct conditions in the use of the product, will provide the best results from its application.
Article from the Australian and New Zealand Grapegrower and Winemaker, Issue 575, 2011, Pages:67-68
Author: Greg Howell
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