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Enzymes in the Brewing Process

Enzymes are complex organic substances that act as catalysts: that is they accelerate the velocity

of a reaction whilst remaining essentially unchanged themselves at the end of it. They promotethe hydrolysis of proteins and polysaccharides into simpler substances, and are usually highly

specific. Each enzyme will act on only a limited range of substrates, frequently on only one.

The main factors affecting enzyme activity are temperature and pH, and to a lesser extent

Calcium, moisture and oxygen. An increase in temperature increases the rate of reaction up to an

optimum that varies from enzyme to enzyme. Above that optimum temperature the enzyme isdestroyed. Individual enzymes also have variable optimum pH ranges. Their activity is optimised

within this range, and inhibited at pH values above and below this range. Enzymes will normally

 be destroyed at pH values far removed from the optimum range. During the germination stage of

malting the formation of many enzymes is promoted and is dependent upon the moisture and

oxygen content of the barley. In the mash, Calcium is essential for the stabilisation of a-amylase,one of the most important enzymes in the brewing process. Without the protection of Calcium

ions a-amylase is rapidly destroyed at normal mashing temperatures. When Calcium is present insufficient amounts the enzyme is stable at above sparging temperatures, only then being finally

destroyed in the Copper.

Much enzyme activity is started in the maltings. The barley is steeped to increase the moisture

content to 42 - 46% and oxygenated to promote enzyme activity in the aleurone layer, all under

controlled temperature conditions. The barley is then allowed to germinate when modification of

the the barley to malt occurs.

Enzymes such as ß-amylase, exo-peptidase and carboxy-peptidase are present in the starchyendosperm of the barley, and are activated during malting. Other enzymes, such as ß-glucanase,endo-proteases, a-amylase and pentosanases are formed in the aleurone layer of the barley during

malting. The formation and activation of these enzymes is promoted by the increasing moisture

and oxygen during the steep, and is then arrested by the kilning. Good kilning should put theenzymes into 'suspended animation' until they are re-activated in the early stages of the mash,

rather than destroying them.

ß-glucanases are highly active during this germination period, breaking down ß-glucan (cell wall

material) into simpler substances. ß-glucanase is highly heat labile, and survives for only a very

short time at mashing temperatures. It is therefore essential to get as much ß-glucan broken downduring malting as possible, since it will cause problems later in the process by increasing

viscosity and wort run-off times and by causing hazes.

The protein specific enzymes, exo-proteases and endo amino-peptidases are again highly heat

labile, and work mainly in the malt-house. Carboxy-peptidases are a little less heat sensitive, andmay continue to operate for as little while in the mash.

The optimum pH range for ß-glucanase and proteases is in the order of 5·0 - 5·5, and

temperature range of 35 - 45° C is optimum. These enzymes then are quickly destroyed in the

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mash when using an infusion mash at 63 - 66° C. However when using decoction mashing

techniques and a much reduced initial mash temperature, significant enzyme activity can occur in

the early stages of mashing. It is for this reason that malts for use in decoction mashing systemsneed not be so well modified as those for use in infusion mashes.

The usual mashing temperature for British beers of 63 - 65° C is as a result of the optimumtemperature for the activities of alpha & ß-amylase, 64 - 68° and 60 - 65° C respectively. Both

are highly active within the normal pH range of wort, 5·2 - 5·5, and the exact temperature of

mash selected by the individual brewer will determine whether the alpha or ß-amylase activity isfavoured during the mash. Calcium ions are required to stabilise the activity of alpha-amylase,

which is an endo-enzyme, cleaving internal a-1, 4-glucosidic links of gelatinised starch.

Alternatively ß-amylase, which does not require calcium for stabilisation, is an exo-enzyme,

cleaving external a-1, 4-glucosidic links to form maltose and ß-limit dextrins. The latter contain a1, 6-glucosidic link, and cannot be cleaved by either alpha or ß-amylase, and so remain in the

wort through fermentation as non-fermentable sugars (Dextrins). The natural enzyme produced

in the wort that will cleave this link is limit dextrinase, but this is highly heat labile and is

destroyed completely at mashing temperatures.

The use of additional enzymes is common throughout the brewing industry, and is greatly beneficial. ß-glucanase is possibly the most common addition, assisting as it does the mashing of

grists containing under modified or unevenly modified corns. It aids Mash Tun run off by

reducing wort viscosity, also improving subsequent beer fineability and filterability. Amylases

are also used, typically where the use of adjuncts may dilute the availability of enzymes in theMash Tun.

Enzyme cocktails, such as Trizyme are formulated to address a range of Mash Tun problems.Use of these products will increase extract, reduce wort viscosity and run-off times, lead to a

 brighter wort ex Copper and improve beer fining performance and head retention.It is possible, if required, to reduce the amount of dextrins remaining in the beer as non-fermentable sugars by the addition of Amylo-Glucosidase, AMG. This enzyme is used in the

Mash Tun and will cleave the 1,6-glucosidic bond to produce glucose. This enzyme finds favour

in the production of high alcohol or low carbohydrate beers. One drawback is that the enzyme isnot destroyed at pasteurisation temperatures and will therefore continue to work in package.

Enzymes are also used in the brewing process post-fermentation, to control chill-haze in packaged beers and increase shelf-life. Such enzymes are proteolytic based on papain (Carica

Papaya) and have an optimum temperature range of 35 - 45°C, and pH range of 4 - 5·5. Added to

conditioning tank they will break down the high molecular weight proteins that react with

 polypeptides to form chill hazes. Whilst other means of inhibiting chill haze are available - forexample the use of Silica Hydrogel or PVPP - Papain remains one of the most cost effective and

widespread means of achieving this objective.