Brewing Process


Beer is an alcoholic beverage obtained by the fermentation or extracts of malted cereals, principally barley, and flavoured with hops and sometimes a percentage of maize and rice. British beer varies from 100% malt to 70% malt plus 30% unmalted cereals, together with sugar, hops, yeast and water.



Most beers consist of over 90% of water. In the old days, brewers would just collect water (always called “liquor” in the trade) locally and make a brew. As certain beers became more widely available through commercial deals and improved transport, their inherent qualities inspired emulation. In the case of the Burton pale ales, the local water is naturally hardened by its heavy mineral content and includes gypsum, which is seen as an important ingredient: breweries producing pale ales a long way from Burton might get their specialists to add the appropriate salts to whatever liquor they used, and to remove any that were unwanted. With top-fermented pale ales, hard water is usually considered an asset. On the other hand, pale lagers in the pilsner tradition use soft water. This also suits the darker ales, such as porter and stout.

Jennings draught bitter from England and Palm Speciale from Belgium have more colour than most so-called pale ales, and both use the soft water relatively untreated.

Before the technology to treat water could be relied upon, breweries tended to be sited near a spring, whose water was less likely to be polluted. Some still use their own spring water, though most recent arrivals take the local commercial product, which they can adjust, as necessary.


From the beginning, malted barley has been a staple ingredient of beer. By medieval times, the techniques of steeping the barley in water to germinate the seed and turn starch into sugar, then applying heat by kilning it, had already become established. The processes have since been mechanized, automated and computerized, but the principles remain much the same.

After harvesting, the barley is bought by the malsters, who can keep it stored under slightly damp conditions for about two years, moisture being essential to stop the barley from deteriorating. Barley for malting is steeped in large vats and brought up to 44% moisture in controlled stages: steeping is interrupted from time to time, the water drained and the carbon dioxide gas given off replaced by air, which allows the grain to breathe and start producing enzymes.

In traditional floor maltings, the malt is then tipped on to the floor and moisture and temperature are again tightly controlled, while the seed germinates and continues to grow the embryo that will eventually convert to sugar when the beer is mashed. The final stage is the kilning that preserves the embryo in the state required for this conversion. Heat from the kiln dries the malt down to 2.5% moisture and cures it to provide the flavour brewers look for.

That describes how pale malt, by far the largest part of the mash in most beers, is produced. Such specialities as black, chocolate, crystal and amber malts may be added. Crystal malt imparts colour to bitters. Instead of being kilned, it is transferred in relatively small amounts to a roasting vessel in which the heat steadily increases while the starch converts to sugar. At the precise moment a clear, sugary liquid is obtained, the maltster cuts off the heat and douses the malt with water in order to preserve it in that state. Malts used in darker beers are kilned in the usual way, and then roasted to the required degree of colour and flavour.

The techniques of ale brewing in Britain were based on malt that is fully modified and has low nitrogen content, thus preventing unwanted haze in the finished product. Throughout much of mainland Europe, the barley, grown in a sunnier climate, was higher in nitrogen, so the malt tended to require more complex procedures at brewery to reach the same result. This influenced the techniques developed for mashing lager, which from start to finish took much longer at lower temperatures, and needed malt with a higher nitrogen content to produce enzymic activity throughout this period.

Today, the big high-tech brewers of ale simply obtain whatever malt meets their price and let their machines and accumulated expertises do the rest. By contrast, many of the new small brewers have discovered the advantages of paying a bit more for high-quality malt that is simpler to work with.


Hops are by far the most recent addition to the list of essential ingredients. They were certainly used by brewers in Northern Europe during the 14th Century, when it would have been noted widely that hopped beer tended to keep longest and best of all. Before hops became universal, beer would have been spiced by various plants and herbs, depending on what was grown in the area or was otherwise available locally.

The preservative qualities of hops remain paramount in the making of some Belgian beers, notably the unique lambic, and they are still needed widely as a disinfectant. Lambics apart, however, hops today are chosen primarily for their flavours. Brewers rate hop plants according to their alpha acid content and divide them very broadly into “bittering hops” and “aroma hops”: hops with a level of 8% or higher are generally used only for bitterness while those below this level may combine bittering qualities with less definable aromas. Such rigid distinctions are continually being bent, as brewers experiment by boiling with just one variety of hop instead of trying to blend flavours and by making ales with hops associated with lager, and vice versa. Bitterness levels, as measured in units, depend as much on the quantity used as on the intrinsic quality of the individual hop, while some well-hopped beers are not especially bitter.

Another traditional function of the hop flower was to act as a filter. At the end of the copper boil, the wort passes through a bed of spent hops that filters out floating particles (including stray bits of hop) as it passes through to be cooled and fermented. More modern Systems of filtration by centrifuge (a whirlpool that traps the particles after the boil) have encouraged the use of hop pellets – compressed hops that some brewers prefer to use. Oil concentrates made from hops became a cheaper substitute for the real thing, but the resultant harshness has convinced some brewers either to stop using them in the boil or to reduce their role.


Perhaps the most vital ingredient of the brew, yeast has the lowest public profile. Visitors on organized trips to breweries may be encouraged to chew grains of malt and to extract the flavours from whole hops by rubbing them with their hands. In most cases, though, the yeast used by the brewers will be kept wherever they have isolated it, to reduce the chance of it being infected.

The first yeasts to ferment beer wafted in the air. Those used today in the brewery will be hygienically controlled, brought out only when the wort has been boiled and cooled. Yeast is then added to provide two essential attributes – alcohol and carbon dioxide – without which beer would not be beer. Highly volatile, it reproduces itself and is cared for lovingly by many breweries, which for safety also stock samples in a central yeast bank. They realize that having to use different yeast would alter the taste of well-established beers.

It has traditionally been divided into ale yeast, which rises to the surface of the vessel when fermenting the beer, and lager yeast that sinks to the bottom. Recent innovations include the use of traditional top-fermenting yeasts in sealed conical fermenters (the type once reserved exclusively for lagers) to produce ales. The outcome is a procedural compromise: most of the yeast sinks to the bottom and, though the fermentation time remains about the same, the ale is generally left to condition for longer than usual until racked.


Such terms as “adjuncts” and “additives” have often been uttered with disdain. The German purity law, known as the “Reinheitsgebot”, stipulates that beer should be brewed only with water, malt, hops and yeast, and there are brewers all over the world who follow this precept. Purists once frowned on any deviation that did not reflect long-standing practice – although one cannot, obviously, brew wheat beer without wheat – on the grounds the brewer was trying to cut corners or get away with spending less money. While that has been so in some cases, there are often more valid reasons. Some ingredients commonly used are listed below.

Torrefied wheat – wheat previously “popped”, rather like the puffed wheat found on breakfast tables, and then conditioned by heat and added to the mash, where it reacts with malt in a manner that improves the beers ultimate ability to create and maintain a foaming head when served.

Flaked maize – dilutes the nitrogen produced by malt.

Malted wheat – malted in the same way as barley, wheat forms a significant part of the mash of German wheat beers.

Unmalted wheat – used in such Belgian specialities as Hoegaarden Witbier.

Rice – beers from the Far East, Central and South America and many produced by major brewers in the USA contain rice. It is added to the mash after heat-conditioning and gives beer a soft, clean texture, without too much body.

Caramel – darkens colour.

Sugar – some beers receive a small amount in the mash to add sweetness but more often cane sugar is added either to the boil or just after, eventually combining with the ale yeast to produce a higher proportion of fermented beer in the finished article. This darker-coloured invert sugar contributes positively to ales that lean towards bitterness and strong taste, because it can impart attractive flavours of its own. Conversely, the textures of many full-bodied and malty ales benefit from the presence of unfermented sugar.

Priming sugar – as sugar helps fermentation, it is sometimes added to living beer at a late stage, even as casks are being racked, to produce carbon dioxide. In Germany, perhaps to get round the “Reinheitsgebot”, some beers are given a small amount of wholly or partially unfermented wort (which, of course, contains sugars) during the conditioning period; this is known as “krausening” the beer.

Brewing Processes

The age-old process by which barley produces beer has been subject to much research, from die trial-and-error discoveries of primitive man to the latest advances in engineering and scientific thought. In the modern era of constant technological breakthroughs, almost every aspect of brewing has been revolutionized many times over. Yet the fundamentals never change. Most of the breweries launched during the past decade operate – to a degree that might depend on their equipment or on how big they are – in much the same way as they would have done in the 1890s.

Change is most evident among local giants and multinationals. They have resources to invest in new technology that does more with less and enables them to benefit from the economies of scale. Brewing the same beer in enormous quantities, often in different plants or in several far-flung countries under licence, they require consistency above all. On the other hand, someone brewing a few hundred barrels a week – or even five or ten barrels – values hands-on flexibility, whether or not the technology is state of the art.

A brief description of how beer is brewed can do little more than generalize. Even such differences as exist between the two fundamental processes, brewing ale and brewing lager, are not absolute. Some ales are now fermented in lager-type vessels and are then given time to mature, while the commercial pressure to bring lager in line with ale and reduce the time taken to brew and store it – to get it to the pub and shops quicker, so money comes in faster – puts a high premium on corner-cutting ingenuity. What follows, therefore, gives merely the outlines.


Liquor (water) to be used in the mash is extracted, from spring or tap, in sufficient volume, chemically treated if necessary, and stored ready for use. Malt is likewise prepared by milling, traditionally into particles rough enough to act as a filter when the mash ends. Some of the smaller brewers operating in restricted space receive their malt ready-crushed by the maltster.


The word is sometimes used for brewing tea, a similar if less complex process. Crushed malt (analogous to the tea leaves) is mixed in the mash tun with hot, but not actually boiling, water. Such additives as torrefied wheat may also be introduced. The mix then stews at a temperature of around 65°C (150°F) for at least one hour. In that time, the starch converts to sugar and the residual malt expands and collects at the bottom of the mash tun (just as tea leaves do in a pot). When brewers are satisfied conversion has taken place, they drain the wort and then sprinkle (sparge) hot water over the spent grains to extract the last drops of goodness, just as you can refill an emptied pot of tea and carry on drinking from it.

That describes the simple infusion system of mashing. The big ale brewers of today may crush their malt into powder and, instead of draining it through the spent grains, transfer it to a wort separator that filters it, rather like a coffee percolator. Because filtering takes half as long as draining, the brewery can mash twice as often.

Brewing lager traditionally involves mashing in more than one vessel and at different temperatures. This so-called “decoction” system gets the optimum return from malt that may not have been fully modified, while dispersing any elements that might harm the beer. The mash starts at a very much lower temperature of under 40°C (104°F). At various times, part is transferred to another vessel that heats it to a higher temperature before returning it, and the entire mash ends up in yet another vessel, known by the German word “lauter”, in which the wort is separated from the spent grains.

Under German law, only malt may be used in the mash. Other countries may supplement the malt with such cereals as maize, rice and wheat that do not produce enzymes and therefore do not need so much extra care.


The malt has now done its job, and the next stage involves what could be described as fine-tuning the flavour. The wort drains from the mash tun/lauter tun to a holding vessel, the underback. From there, it is pumped into a vessel commonly referred to as a “copper” or “kettle” wherein it is boiled for around 90 minutes, long enough to allow the flavouring or spicing agents to do their work. The most common of these is the hop, of which different varieties may be inserted into the copper at different times. In general, hops used for bittering are added near the beginning of the boil, while aroma hops are kept back until later.

For whirlpools that remove all traces of the hops by centrifuge before the wort passes on, the more compact pelletised hops are required. In the classic brew house, the hop leaves are needed to filter the wort as it leaves the copper or hopback. To make the wort as clear as possible at this stage, finings made from dried seaweed are added.

Some brewers add hops at the very end: these are immediately swept to the filter bed and contribute to the flavour of the wort as it passes through them. In the brewing cycle, this is the earliest example of the technique known as “dry hopping” – adding hops to beer after the boil. Hops can also be added in this way at various stages while the beer is conditioning and maturing after fermentation. Many breweries dry-hop at the time draught ale is being racked into the cask from which it will ultimately be served, usually adding pre-measured compressed pellets that will settle at the bottom of the cask, along with the yeast sediment, by the time the beer is drawn off in the pub.

Brewing sugar, used by some brewers to help the beer ferment, contributes most powerfully to the ultimate flavour if added to the boil. Some brewers prefer to wait until the boil is over.

Fermentation and Conditioning

After the boil, the wort collects and is cooled in stages, to just under 20° C (70° F) for ale or under 10° C (50°F) for lager, before being transferred to the fermenting vessel into which yeast in liquid form is pitched. Times vary, but the very active ale fermentation, during which the conversion of the wort into alcohol leads to much frothing on the surface and an enticing spread of fruity aromas, takes about three days, plus another three days for attenuation, when any remaining fermentable sugars are converted and the beer starts to mature in this less volatile atmosphere. At the end, most of the yeast lies encrusted at the top of the vessel. The beer now requires another few days to condition in a separate tank (perhaps more for stronger or specialist beers) before packaging.

Lager takes much longer. Primary fermentation, now increasingly carried out in closed conical vessels, lasts for up to two weeks. Compared with ale, the level of activity at the lower temperature is less pronounced, as the yeast sinks to the bottom. The beer is then transferred to the storage (lagering) tanks where, in temperatures around freezing point, it matures for weeks, even months. Before they are ready to be packaged, beers may undergo further processing. Filtration removes all or most traces of yeast, while pasteurisation sterilizes the beer. In both cases, the removal of yeast means the beer is no longer “alive” because it has stopped producing carbon dioxide. CO2 has to be added to preserve the beer until the keg is tapped or the bottle or can opened.

Brewing process


In the UK, a substantial amount of bulk beer leaves the brewery in living form, so that the final version of the beer is not determined until the moment of drinking. Barrels carrying it are referred to as casks: hence the terrn “cask-conditioned” defines beer that continues to ferment as it leaves the brewery and while it sits in the cellar of the pub, cafe or restaurant. Because the finished article needs to be clear in the glass, finings in liquid form, made traditionally from the swimbladders of sturgeons, are poured in at the racking stage before the cask is sealed. These finings enable all the sediment to sink to the bottom of the cask once it has been made ready for serving. Some brewers also dry-hop the beer in the cask to impart a final touch of flavour.

Casks containing beer that has been filtered and/or pasteurised are known as kegs – the shapes may be identical (in that an increasing number of “casks” are kept upright in the cellar, as are all kegs), but the essentials differ. Living beer needs containers with an orifice from which excess CO2 can escape, otherwise the cask would eventually blow up. Beer wholly conditioned in the brewery requires an inlet for the gas cylinder that will help raise it to the bar.

Beer not packaged in bulk goes into bottles or cans. The growing popularity of beer for home consumption has been founded on packs of cans, but bottled products have retained their position in many countries, and have notably regained some of their former stature in the UK, mainly at the top end of the market. Compared to the time when UK brewers sold considerable amounts of bottled beer in their own pubs, usually to be mixed with draught beer, and expected the empties back, most of the trade today is away from the pub and in non-returnable bottles.