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Enzymes are defined as complex biological catalysts of a protein nature, which trigger reactions without being modified by them or appearing in the final product.
They activate and deactivate under certain conditions, and the mashing process is responsible for manipulating those conditions. The enzymes involved in beer brewing are created inside the grain during the malting process.
The maltster makes the grain believe it’s time to sprout by moistening it and initiating germination. Inside the barley grain, nature has arranged a multitude of enzymes ready to help the shoot develop.
Which enzymes matter when making beer?
The enzymes that interest us are those that break down the grain’s starch and allow the shoot access to the resulting sugar as food, until the plant reaches the surface and can generate its own food through photosynthesis.
Those enzymes created during germination and drying are used by the brewer to convert the ground malt into a sweet liquid during mashing.
The sweet liquid is separated from the grain and all available sugars are collected during the sparging process. This liquid is then boiled in the kettle with hops to finish making the wort.
Once cooled, it is inoculated with yeast and once fermentation is complete, we have beer.
| Enzyme | Function | Optimum | Range | Effects on beer |
| Proteases | Degradation of large proteins | 45 – 55°C | 37 – 55°C | Contributes body and head retention. |
| Peptidases | Release of amino acids | 45 – 55°C | 37 – 55°C | Facilitates fermentation and improves haze. |
| Beta-glucanases | Degradation of beta-glucans | 37 – 45°C | 30 – 45°C | Reduces viscosity, prevents thick worts. |
| Alpha-amylase | Liquefaction of starch to dextrins | 70°C | 63 – 70°C | Increases body and mouthfeel. |
| Beta-amylase | Conversion of starch to fermentable sugars | 60 – 65°C | 55 – 65°C | Drier beer with higher alcohol content. |
Table 1: Temperature and enzyme activity
Proteolytic and diastatic enzymes
This is a simplified version of what happens before and during beer brewing. The enzymes that matter to the brewer are those that can be controlled.
These are the proteases or proteolytic enzymes, which, as their name implies, degrade proteins. The other group of enzymes we want to control are the diastases or diastatic enzymes, which degrade starch.
Protein molecules are long, complex chains containing nitrogen. They are made up of amino acids linked in three-dimensional chains with thousands of atoms.
The proteolytic enzymes in malt reduce those chains in a way that benefits our beer. Proteins are very important to us; to begin with, yeasts need free amino acids for their development.
Some proteins that remain in the beer are responsible for body and mouthfeel. Others are responsible for foam formation and head retention.
There are also those that produce haze in the beer. Finally, the nitrogen in proteins combined with carbohydrates during malting is responsible for many of the beer’s flavors.
Protease and peptidase enzymes
There are two groups of proteolytic enzymes that are important in the beer-making process: proteinases or proteases, and peptidases.
Proteases break down large protein molecules into smaller amino acid chains, which promote head retention and reduce haze.
Peptidases release individual amino acids from the ends of proteins, which serve as food for yeasts. The process in which proteolytic enzymes are activated is known as the protein rest or proteolytic step.
Most of the proteins in the wort are not soluble until they reach the temperature range of 45 to 55°C for the protein rest.
The range of the two enzymes overlaps, but the ideal temperature for a protein rest is 50°C.
Enzymes denature at temperatures above 65°C. The ideal pH range is slightly lower than the normal mash range, from 5.2 to 5.8, but within this interval they work quite well, so you shouldn’t go to the trouble of lowering the pH.
| Enzyme | Optimum pH | Action |
| Proteases | 5.0 – 5.2 | Enables protein degradation. |
| Peptidases | 5.0 – 5.2 | Aids in the release of amino acids for yeasts. |
| Beta-glucanases | 5.2 – 5.5 | Prevents viscous worts. |
| Alpha-amylase | 5.6 – 5.8 | Promotes a greater presence of dextrins. |
| Beta-amylase | 5.2 – 5.5 | Improves fermentable sugar production. |
Table 2: Optimum pH for brewing enzymes
1. Protein rest
The protein rest is not as necessary now as it once was, since most malts are fully modified.
A longer malting period allows the proteolytic enzymes to degrade the malt proteins to a certain extent, so the protein rest is not widely used today.
If you are making very cold light beers, using under-modified malt, or using a high proportion of flaked or unmalted grain (>25%), then a protein rest can be worthwhile.
Performing a protein rest with well-modified malts can lead to the degradation of proteins responsible for head retention or body, resulting in a watery, foamless beer.
2. Temperature
There are other proteolytic enzymes working in this temperature range, known as beta-glucanases. What they do is degrade the beta-glucans present in the grain husk, as these can cause problems by creating a viscous, dense wort if they are not broken down.
When using more than 25% unmalted grain, a rest between 37 and 45°C — which is below the protein rest — for 20 minutes can be worthwhile, to break down the beta-glucans without affecting the proteins that contribute to body and head retention.
Diastatic enzymes
Diastatic enzymes degrade and convert starch (the grain endosperm) into fermentable sugars and non-fermentable dextrins.
Our interest centers on two diastatic enzymes that are active during mashing: alpha-amylase and beta-amylase.
These enzymes work together to break down these long, complex chains of soluble (or gelatinized) starch into sugars and dextrins.
Starch molecules are essentially long chains of glucose molecules, but due to the bonds between them, they are not fermentable.
Dextrins have long chains with four or more glucose molecules and are by-products of fermentation. They are not fermentable and have no flavor; however, they contribute body and mouthfeel to the beer.
Alpha-amylase cuts starch molecules randomly into pieces that beta-amylase can work on. Until these molecules are broken down, they are not fermentable and are known as dextrins.
What alpha-amylase does is a process known as liquefaction. It physically liquefies the starch, preparing it for further enzymatic action.
1. Mash programs
Mash programs that encourage alpha-amylase activity (optimum at 70°C) produce a wort with a high percentage of non-fermentable sugars, or dextrins.
The beer produced this way is full-bodied, with a denser body and more mouthfeel. Beta-amylase degrades starch and dextrins into glucose (one molecule), maltose (two molecules) and maltotriose (three molecules).
Once beta-amylase has acted, the starch has been reduced to fermentable sugars.
Mash programs that favor beta-amylase activity (optimum between 60 and 65°C) produce a highly fermentable wort. The resulting beer will have a drier palate and a higher alcohol content.
2. Temperature
It is important to understand that, although each diastatic enzyme has an optimal temperature, both will work over a relatively wide temperature range and, most of the time, enzyme activity overlaps.
Both alpha-amylase and beta-amylase will work together between 63 and 70°C. So, in general, if you want a lighter-bodied, drier, more alcoholic beer, you can mash at the low end of the range.
If you want a fuller-bodied, more dextrinous beer, you should mash at the upper end, but intermediate mash temperatures around 67°C are usually adopted.
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Frequently Asked Questions (FAQ)
1. How does water pH affect enzyme efficiency during mashing?
pH is critical because it determines the three-dimensional shape of enzymes and their ability to bind to starch. Although the general range is 5.2 to 5.8, a pH close to 5.2 favors beta-amylase activity, resulting in more fermentable worts. Conversely, a slightly higher pH (5.7–5.8) benefits alpha-amylase, ideal for fuller-bodied beers. If the pH moves outside these ranges, enzymes denature, drastically reducing extraction efficiency.
2. What happens if the protein rest is exceeded with modern malts?
Performing a prolonged protein rest (45–55°C) with “well-modified” malts (most modern base malts) is counterproductive. The proteases will excessively degrade the long-chain proteins that are essential for head retention and beer body. The result will be a “thin” beer with a quickly dissipating foam crown and a watery mouthfeel.
3. Why did my beer turn out too sweet despite mashing at the correct temperature?
This is usually due to premature deactivation of beta-amylase. If the mash temperature accidentally rises above 70°C (even for a few minutes) before stabilizing in the lower range, the beta-amylase denatures permanently. Without this enzyme to create maltose, alpha-amylase will only produce non-fermentable dextrins, leaving a wort with a high final gravity and excessive residual sweetness.
4. When is a beta-glucanase rest strictly necessary?
This rest (37–45°C) is indispensable when using proportions above 25–30% of unmalted adjuncts (such as wheat, oats or flaked barley) or six-row malts. Beta-glucans are gums that increase viscosity; without enzymatic breakdown, the brewer risks a stuck mash, where the liquid fails to drain through the grain bed during sparging.
5. What is “diastatic power” and why is it important for enzymes?
Diastatic power is the measure of the enzymatic reserve a malt possesses to convert starch into sugar. Base malts (such as Pilsen or Pale Ale) have high diastatic power and can convert their own starches and those of adjunct grains. However, specialty malts (caramel, roasted) have lost their enzymes due to the heat of roasting; if a recipe has too many adjuncts and too little base malt, there will not be enough enzymes to complete conversion, leaving residual starch in the beer.
