Firstly, the barley grain is steeped to increase water content to around 40%.
Secondly, the grain is germinated by incubation at 15-25o C for 3-6 days when enzyme synthesis is stimulated under the control of gibberellins. During this time the alpha-amylase levels rise significantly, although beta-amylase levels remain low. The combined action of these two amylases results in an increase in fermentable reducing sugars. This is traditionally expressed as the diastatic power, DP, which rises from around 80 to 190 in 5 days at 12o C.
Lastly, the malt is kilned. Kilning involves warm air drying the malt at 40-60o C rising to 60-80o C. This results in a reduction in water content to 5%, a cessation of respiration and growth and a controlled development of colour in the malt. There is also a loss in enzyme activity during kilning.
Mashing
Mashing involves heating the ground malt in water to extract and hydrolyse starches to fermentable sugars. Mashing is carried out by two general processes:
Infusion mashing, where the mash is held at 65o C.
Decoction mashing, where the temperature is gradually raised.
During mashing, amylases hydrolyse the starches to produce fermentable sugars together with "limit dextrins". These are the result of the inability of the amylases to hydrolyse the branch points in the starch and they persist in the final beer where they give both body. Alpha and beta amylases are often added at this point in order to boost the natural enzyme content. In the production of certain types of beer, such as "light" beers, it is desirable to degrade these limit dextrin’s to produce a beer with a higher alcohol and lower carbohydrate content. This is accomplished by the addition of pullulanase, which can degrade the alpha 1->6 branches:
During malting, a beta-glucan is solubilised from the cell walls, and this is frequently incompletely hydrolysed during malting. If this beta-glucan persists during mashing, it results in unacceptably high viscosity in the brewing liqueur, or wort. For this reason, beta-glucanases are often added to reduce wort viscosity. The most common sources of this enzyme are Bacillus subtilis, B. amyloliquefaciens or Aspergillus niger. Very high levels of hydrolysis are achieved and this activity persists through to the final product as the beta-glucanase is very stable.
Beta-glucanase
Conditioning
Conditioning is necessary to prevent the formation of chill haze, a protein-polyphenol complex containing some carbohydrate. This is prevented by the addition of proteases, most commonly papain:
Papain
Papain treatment is carried out at 4o C for 3-4 days. The process must be carefully controlled or excess proteolysis will occur, altering other properties of the beer such as foaming and head retention.
Other enzymes are sometimes added to beer, such as glucoamylase which is used after primary fermentation to degrade limit dextrin’s resulting in maximum alcohol content and a sweeter beer.
Enzymes are added to beer as soluble additives, but some work has been done with continuous conditioning based upon immobilised enzymes. This has yet to make any commercial impact.
Conclusion
In conclusion Enzymes are vital in all the different stages of the brewing process from the start to the finished product. There are a large amount of enzymes that are used and occur naturally in process. Without them beer wouldn’t exist and the different use of enzymes along with other factors gives different beers there individual strength and taste which draws people with all different tastes to the pup every weekend.
