Traditional Commercial Brewing
07 October 2010
Read about traditional commercial brewing in Great Britain, about all the processes of brewing (malting, kilning the malt, mashing, boiling, cooling, aeration, fermentation, maturation and barrelling, drinking). Also there is information about different fermentation systems: single vessel skimming system, carriage-cask cleansing system, puncheon cleansing system, dropping system, patent union cleansing system, Yorkshire stone square, conical fermenter.
Read also:
Home Brewing. Water and Water Treatment
Home Brewing. Mashing and Sparging
Traditional malting
The primary ingredient of English ale is malted barley. In days long past, all breweries malted their own barley, and this was performed in a traditional floor mailings. Harvest time was an extremely busy period for the maltsters because a whole seasons' supply of barley would begin to arrive from the local farmers in a seemingly never ending stream. The barley had to be malted as soon as possible after harvesting because the grain would rapidly deteriorate during storage, particularly if it was damp. If damp, the grain would continue to respire during storage causing destructive temperatures to be developed in the centre of the bulk, whereas in the cooler regions partial germination may take place thereby ruining its brewing properties. Furthermore, any pests collected with the harvest would continue to attack the grain. However, the barley arrived in too great a volume to be malted immediately.
The maltsters first task was to partially dry the grain as it arrived and put it into temporary storage in readiness for malting. Drying was performed by spreading the grain on to the malting floors and opening ventilators in the side of the building. This caused an air flow across the surface of the grain. The grain was turned over frequently to ensure even drying. Drying retarded respiration and eliminated the possibility of mildew. Successful long-term storage of barley for brewing purposes requires that the moisture content of the grain be between certain limits. This was difficult to estimate, and besides, with floor drying and manual turning it was well nigh impossible to ensure uniform moisture content throughout the bulk. To be safe, the maltsters of yesteryear were forced to malt the barley as soon as was practical, and as soon as the grain was safely in store, the malting season began in earnest.
Before the malting of a quantity of barley was begun it was first graded by means of "Boby's screens", so named after the man who devised the first automatic grading machines. These were nothing more earth shattering than a series of mechanically actuated sieves. The screens had the effect of removing stones, leaves, and other debris, and performed the important task of grading the grain into its various sizes. A uniform grain size is important because the maltster requires that ail of the grain in any one batch should germinate at the same rate. After the screening operation the grain was stored in garners, which were large storage boxes situated on an upper floor above the steeping tanks. The steeping tanks were known as cisterns or steeps.
At the start of malting a batch of barley, trap-doors were opened in the storage gamers and a quantity of grain was allowed to flow by gravity into the cistern situated on the floor below. The grain was steeped in the cistern until it had absorbed enough water to begin germination. During the steep the water was changed several times, partly to wash the grain clean, but primarily to ensure that the water contained an adequate supply of dissolved oxygen for the germination process.
After the grain had taken on water it was removed from the cistern and spread on to the growing floor of the makings to continue with the germination. The process of germination caused heat to be evolved and the grain was maintained at about 15°C by varying the depth of the grain on the floor. If it was too hot it was spread out further across the floor, or heaped up more thickly if it was too cold. The grain was frequently turned over by the maltsters to maintain a constant temperature throughout the bulk, thereby ensuring even germination.
During germination rootlets sprout from the barley and germination was deemed to have proceeded far enough when these rootlets had grown to a particular length. Towards the end of the germination phase the grain was piled high in order to increase the temperature of the bulk to about 22°C. It was turned rather more frequently and ventilators were opened close to the floor of the malt house which caused an air flow across the surface of the grain. This partially dried the green malt and arrested germination in preparation for the kilning phase.
The point at which germination is stopped varies according to the type of malt being produced. A malt is known as well modified if germination has been allowed to proceed for a long period, and poorly modified or partially modified if germination is stopped after a short period of time. English brewing favours the use of well-modified malts, whereas Continental practice traditionally favoured the use of poorly modified malts. Poorly modified malts require the use of the Continental decoction mash process during brewing in order to complete the modification and to reduce the nitrogen/protein content of the malt to acceptable limits.
Kilning the malt
After the germination phase the malt then enters the kilning phase of its production. The kilning phase dries the malt which arrests germination completely and colours the malt. Different degrees of kilning produce different coloured malts with correspondingly different flavours. The range of malts vary from pale malt, which is the staple ingredient of ail English ales, through amber and chocolate malts to black malt which is roasted almost to complete destruction.
The kiln had a perforated floor under which a fire was maintained. Prior to the pale ale revolution in the mid 1800s, the most common type of malt was brown malt. Brown malt is a smoked malt, kilned over a fire of damp hardwood such as oak, beech, or hornbeam. The damp wood smoked profusely, the smoke percolated through the perforated floor and smoked the malt. There was some pale malt made in those days, but pale malt had to be kilned over a clean fire of charcoal or coal, both of which were prohibitively expensive and pale ales were therefore only drunk by the rich. Coal was expensive to transport and attracted a coal tax, therefore pale malt only became economic in the early 1800s when the industrialisation of Britain demanded cheap and plentiful supplies of coal.
There are some active floor makings still in existence, but they are very rare. These days the majority of brewing malt is made, not by the breweries, but by the large commercial maltsters who employ modern techniques and automation to enable them to process large volumes of barley very quickly and economically. There are several "scientific" acceleration techniques that can be applied to considerably speed up the malting process, such as gibberellic acid treat-ment. I suspect that modern malting technique may leave a lot to be desired as to the brewing qualities of the malt thus produced, but it is not difficult to understand why the breweries have abandoned their makings in favour of the white-coated, high-speed, push-button mass producers.
At the turn of the century, Bass had three breweries at Burton upon Trent. To supply these breweries with malt, Bass also owned a total of 42 malting houses, the buildings of which covered a combined area in excess of some 400 acres. These makings required the services of some 450 semi-skilled men for about four months of the year (the malting season). It is obvious that malting was not only very expensive in both labour and property, but with the rushed nature of the malting season, and the temporary hiring of a substantial number of semi-skilled men, it was also quite an extensive logistics problem for the breweries. Incidently, the temporary maltsters were usually farm workers who in those days invariably found themselves redundant from the harvest until the next spring.
In the brewery
The shape size and layout of traditional breweries vary considerably depending upon their capacity the traditions and technology of the time that they were built, and the extent of alterations and enlargements made over the years. They range from the gigantic five-storey factory type buildings typical of the large brewers of London and Burton upon Trent, which from the outside are not much different in appearance to any other large 19th century factory, to the quaint Victorian tower breweries which were typical of the smaller country brewers.
Before the malt can be used for brewing it must first be cracked or milled. This is normally performed by passing the malt between two or more sets of steel rollers, rather like an old-fashioned washing mangle. The cracking of the malt fractures the grain to enable the water in the subsequent mashing process to reach the starches contained within the malt. Cracking of the malt is not normally performed until it is ready to be used for a brew because should the malt become even slightly damp during storage it will become slack and be unsuitable for brewing. After milling the malt is mixed with the other malts or malt adjuncts used in the recipe and is now called grist. It is passed to the grist case where it is held in readiness for mashing. The grist case is often heated and is situated above the mash tun.
Water for brewing
The water used for brewing is often drawn from the brewery's own well. It is pumped from the well into storage tanks in readiness for use. There is often a separate water treatment tank where the water is treated to give it a composition appropriate to the type of beer that is being brewed, a process known as Burtonising. Brewers call their brewing water liquor to distinguish it from the water used for washing etc. The relative mineral content of the liquor affects the subsequent mash and has an important bearing on the outcome of the final product: Different water compositions favour different types of beer.
The mash
Mashing is the process of extracting fermentable sugars from the grist by steeping it in hot water for about two hours, this operation being performed in a vessel known as a mash tun. During the mash, enzymes contained in the malt convert the starches into fermentable sugars, a reac-tion known as saccharification. The enzymes responsible for saccharification are temperature sensitive, and therefore the temperature of the mash must be maintained as closely as possible to its ideal of about 66°C. If the mashing temperature is too high, the enzymes responsible for conversion may be destroyed, whereas if the temperature is too low an inefficient mash may result. The temperature of the mash must be maintained within about 3°C throughout the two-hour mashing period. The brewers relied upon good thermal insulation of the mash tun to prevent excessive heat loss during the mashing period.
The English mash tun that has evolved over the years is a large cylindrical vessel which is usually unhealed but nevertheless well insulated. It is fitted with an insulated cover and is often fitted with rotating mechanical stirrers known as Armstrong rakes or porcupines. These serve to mix the grist into a thick mushy paste and ensure that there are no dry pockets.
Obviously, the action of mixing the cool grist with the hot liquor lowers the temperature of the overall mash somewhat, The ideal starting temperature of the mash is around 66°C (initial heat), but the grist needs to be introduced to liquor which is at a higher temperature, about 75°C, known as strike heat, to compensate for the drop. If the strike heat is too high some of the conversion enzymes in the malt may be destroyed, and yet if the initial heat is too low an inefficient mash may result Some breweries ease this problem by heating the grist prior to its introduction to the liquor. In these breweries the grist case (the hopper above the mash tun which holds the grist in readiness) is heated to reduce the important temperature differential between strike heat and initial heat. This allows the use of a lower strike heat, and consequently reduces the potential for errors.
At the start of a brew a quantity of hot brewing liquor is run into the mash tun. When the liquor in the mash tun has cooled to strike heat the grist from the grist case is allowed to flow into the mash tun, and the porcupines are set in motion and allowed to run for two or three revolutions, after which they are turned off. In some breweries the grist is pre-mixed with the mash liquor before entry to the mash tun using a device called a Steele's pre-masher. This is an archimedean screw affair enclosed in a tube, the grist case being at one end, and the whole contraption is mounted above the mash tun. The grist is carried to the mash tun by means of the archimedean screw, but about half way along it meets a jet of mash liquor maintained at an appropriate strike heat. The Steele's masher has the effect of ensuring that the grist is well mixed with the liquor, avoiding dry spots and eliminating the need for Armstrong rakes, although they are usually also fitted. The pre-masher also helps to reduce the critical difference between strike heat and initial heat.
When the grist and liquor have been introduced to the tun and well mixed, the porcupines are turned off and the mash is allowed to stand for one-and-a-half to two hours. If the temperature of the mash falls too much it can be raised by running some more hot liquor into the bottom of the tun, a process known as underletting. When the mash has proceeded far enough, the process is often halted by raising the temperature to about 77°C. This is done because the subsequent running and sparging operation is a slow one, and can take two hours or more. If the process was not halted saccharification would continue until the boiling phase, with the result that the grain would be over mashed. The temperature is usually raised by underletting, but this has the danger of diluting the ale too much, and some breweries do not bother.
When the mash is complete, taps are opened in the bottom of the tun and the sweet wort is allowed to run off into a receptacle known as a spendsafe. The goods in the mash tun settle down on to a mesh that covers the bottom of the tun. The goods act as a filter bed for the sweet wort which removes solid particles and debris. The first runnings from the mash are usually turbid and are returned to the tun until it runs bright, at which point it is directed to the under-back. The underback is a heated holding tank which collects the sweet wort in readiness for the boiling phase. The wort must not be allowed to cool before the boiling phase otherwise off-tastes and hazes may be produced in the finished ale.
When the sweet wort has been run off, the goods in the mash tun still retain much of the sugary matter, and this must be flushed out. This is performed by a process known as sparging, originally referred to as fly-mashing. The mash tun is equipped with rotating perforated pipes known as sparge arms. These operate in much the same way as a domestic lawn sprinkler and gently spray hot water, at about 77°C, on to the grains to flush out the remaining sugars. The specific gravity of the spargings is monitored and sparging is halted when this falls below about 1005. Over-sparging extracts undesirable substances from the grains which cause off-tastes and hazes, apart from the risk of over diluting the wort. The sweet wort is then directed to the copper for the boiling phase.
Sparging was not introduced until the mid 1800s. Before that time the goodness was flushed out of the grains by re-mashing. After the first mash the wort was run off and this was used to make the stock ales of about og 1110. The same batch of grain was then mashed a second time, and the runnings from this was used to make the common ales of around og 1080. Usually the same batch of grain was then mashed a third time, and this was used to make "small beer" of around og 1050. These gravities were typical of most beers until close to the turn of this century. The system was very flexible indeed. The three worts could be brewed separately to produce three ales of 1050, 1080, and 1110, or they could be used in any combination to produce a whole range of ales and beers. In busy periods common ale could be produced in greater volume by combining the first and third worts, or by combining all three worts; this will produce common ale of og 1080 at three times the usual volume. A strong ale of og 1095 can be pro-duced by combining the first and second worts, and a session beer of og 1065 can be produced bv combining the second and third worts. A range of five beers could thus be produced.
The boil
During boiling, bacteria contained in the wort is destroyed, haze forming proteins are precipitated out of solution, undesirable volatile substances are driven off, and a series of complicated chemical reactions take place, all of which improve the quality of the final product.
At the start of the boil the hops are added and about half way through the boil any brewing sugars used in the recipe are added. During the boil some of the flavour and aroma giving substances of the hops are driven off, therefore about twenty five percent of the hops are often held back until the last fifteen minutes of the boil. Copper finings are often added towards the end of the boil. This is usually carragheen, commonly known as Irish moss, but is in fact a seaweed. This helps to coagulate the proteins in the wort and assist in their precipitation out of solution. A very vigorous boil is desirable in order to drive off the unwanted volatile products, precipitate protein, and extract the hop products.
Traditionally the copper was heated by wood or coal, but from early Victorian times onwards this was gradually replaced by superheated steam. The very first recorded use of superheated steam for industrial processes was installed in Hartford's London brewery in 1785, by the incredible inventor Joseph Bramah.
Cooling
When the boiling phase is complete the wort is run from the copper into a receptacle called the hopback. This removes the spent hops from the wort, the hops settle on the bottom of the vessel and act as a filter bed which filters the trub (precipitated protein matter) out of the wort. The wort must then be rapidly cooled to pitching temperature. This not only helps to keep bacterial
infection at bay, but also forces further precipitation of protein matter out of solution. Cooling was traditionally performed by very large flat open cooling trays situated at the top of the brewery the cooling being performed by the simple means of atmospheric evaporation. Later the cooling process was speeded by passing cold water through pipes situated in the trays, and eventually this was used in conjunction with a device which brewers called a refrigerator in which the wort was allowed to trickle, like a waterfall, over a series of pipes through which cold water was pumped. Open trays and waterfalls exposed to the atmosphere are an open invitation to bacterial infection with modern low-gravity worts. A modern form of cooler is a heat exchanger, usually referred to as a paraflow, in which the wort meets a counter current of cold water, separated from it by means of very thin copper, or stainless steel baffle plates.
Once the wort has been cooled it may be left to stand for a while to allow more trub to settle, or the trub may be removed by means of a whirlpool, a circular chamber that sets up a cyclone in the wort which removes the trub by drawing it into the eye of the whirlpool.
Aeration
The boiling phase of ale production drives off the dissolved oxygen in the wort, but the yeast needs oxygen during the Initial aerobic growth phase prior to alcoholic fermentation so some oxygen must be put back. Open trough coolers absorb some air through the exposed surface of the wort, and refrigerators promote the absorbtion of copious amounts of air due to their water-fall action. Paraflows are totally enclosed. The wort is not given the opportunity to absorb air, and therefore air needs to be introduced into the wort by some other method. In some breweries air is introduced into the wort at the time of filling the fermentation vessel by spraying the wort through roses, thereby admitting atmospheric oxygen. Other breweries blow filtered air into the fermentation vessel, or into the cold end of the paraflow.
Fermentation
The wort is directed from the cooler to the fermentation vessel. Here the volume and temperature of the wort are adjusted by adding hot or cold liquor as appropriate. The yeast is then added (pitched) and the volume and specific gravity of the wort are measured and recorded for excise purposes.
The temperature at which fermentation is conducted is obviously important. English ales are typically fermented between 18 and 22°C. Too high a temperature and off flavours or yeast bite may result, too low a temperature and the yeast will not work efficiently. The process of fermentation causes heat to be generated which could raise the temperature of the wort above acceptable limits if left unchecked. This temperature rise is not apparent in the small volumes used in home brewing, but is quite substantial in the large volumes brewed by commercial brewers. The temperature of the fermentation vessel is controlled by means of attemperators. These are coils of piping set round the inside of the fermentation vessel through which water can be pumped to maintain the temperature of the wort between normal limits.
During fermentation the the heavy sugars in the wort are converted to lighter alcohol, causing the specific gravity of the wort to progressively fall. This fall in specific gravity is called wort attenuation.
When the wort has attenuated to racking gravity the fermentation is stopped by pumping cold water through the attemperators and lowering the temperature. The fermentation is stopped at this stage to ensure that there is sufficient fermentable material remaining in the wort to promote a rapid secondary fermentation in the casks. The cooling also has the beneficial effect of causing most of the remaining yeast to sediment out. Some breweries allow fermentation to proceed to final gravity before racking.
Fermentation systems
There are various fermentation systems that have been developed over the years. The major difference between most of them is the method by which surplus yeast is removed from the beer. It has been known since time began that the lower the amount of yeast in a beer after fermentation, the brighter, clearer, cleaner, and more stable the beer will be. Furthermore, if exhausted or dead yeast is allowed to drop into the beer it may become yeast bitten, producing harsh off flavours and cloudiness. At the end of fermentation, as fermentation activity subsides, the whole yeast head is in danger of dropping into the beer unless it is removed. Fermentation systems come in three basic varieties; skimming, cleansing, and dropping.
Single vessel skimming system
This is the simplest of all fermentation systems and. historically, probably the most primitive. The wort is collected and fermented in a single open vessel known as a square or a round depending upon its shape. The first head of yeast brings up with it sludge, trub, and hop matter which forms on the top of the froth. When the yeast head has established itself sufficiently this flocculum is carefully skimmed off. Some breweries of old used to skim every twelve hours thereafter, but this was probably overdoing things a bit. When fermentation is nearing completion the yeasty head is skimmed off completely and the final head, known as the 'seal', is allowed to form. The casks are filled directly from the fermentation vessel.
Beers fermented using this method tend to be rather yeasty in flavour. The old Everards brewery at Burton upon Trent used this system, as do many of the new mini-breweries, such as Ringwood brewery in Hampshire.
As an alternative to filling casks directly from the fermenting vessel, some breweries transfer the beer to a racking tank, leave it to stand for a few hours to permit any extraneous bits and bobs carried across to settle out, and fill the casks from this. A modern fermenter would be made from stainless steel and would have automatic cleaning and sterilising apparatus fitted. At the end of fermentation the yeast is skimmed by a vacuum scavenger and the beer is then cooled. The cooling causes more yeast to drop out of suspension and settle out on the bottom of the vessel, at which point the beer is transferred to the racking tank, and then into casks.
Carriage-cask cleansing system
Often referred to as the farmhouse system, this method is an adaption of a primitive home brewing method which has probably been used since time began, although it is not used these days. It was used almost universally by home brewers and small commercial breweries from, perhaps; Elizabethan times up until the beginning of this century. It was a technique for cleansing ale of its yeast and reputedly produced superior and more stable ale than that produced from the simple skimming system mentioned above. The cleansing operation was performed in cleansing casks.
Fermentation was started in an open fermenter, but towards the end of fermentation the partially fermented beer was run into a number of cleansing casks and fermentation was completed in these. The casks, which were supported on still ions above a wooden trough, were filled to the brim with the actively fermenting beer. The action of fermentation forced yeast and beer out of the bung hole, which ran down the side of the cask and into the trough below. The trough was at a very slight incline which caused the beer to separate from the yeast. The casks were kept full to the brim by topping them up with beer from the trough every two or three hours, day and night. This continued for two or three days until fermentation had ceased, at which time the casks were bunged down and put into storage.
Apart from cleansing the ale of its yeast an additional advantage of this system, in the days before cooling techniques were introduced, is that by splitting the fermenting ale into smaller units the heat generated by fermentation was more readily dissipated, and a cooler ferment was possible.
Beer losses were high due to spillage and evaporation. It is the method used by the brewer of Kingston ale in the contemporary passage heading chapter five, and as can be seen, he lost two out of twenty-six barrels during cleansing. It was the technique advocated by William Cobbett in his essay on home brewing written in 1821, and was almost standard practice by small brewers of the eighteenth and nineteenth centuries. However, it was too cumbersome to be used by the large breweries due the labour involved in perpetually humping casks around and this apparently gave small country brewers a quality advantage over their larger cousins.
This system was still in use by Batemans of Wainfleet up until 1953. Wooden cleansing troughs are visible in a photograph of Brakspear's brewery, taken at the turn of this century, but they were simply being used as still ions for casks during manual bottling, and were obviously not in use tor cleansing purposes.
Puncheon cleansing system
Sometimes referred to as the Butt system, this is a slight modification of the basic carriage-cask cleansing system described above and is identical to it in most respects, in the previous system the beer was cleansed in the carriage casks, that is, the trade casks which would be used to deliver the beer to the pub. In the puncheon system, instead of using carriage casks, cleansing was performed in larger, fixed, static puncheons or butts, situated over a trough as previously. When cleansing was complete the beer was racked from the puncheons into the trade casks.
Because large static puncheons are employed, greater volumes are accommodated and there is much less manual rolling around and stillaging of casks making the system more suitable for large breweries. However, the puncheons still needed to be topped up every couple of hours, requiring a servant in attendance twenty-four hours a day, the beer losses were still high, around ten per cent, and large puncheons are difficult to clean properly without disassembling the cask. Although it was an improvement over the previous system it was still cumbersome for very large breweries to operate. However, an advantage of the system was that the beer was racked off any sediment that forms during cleansing, producing a cleaner beer.
The dropping system
The skimming system is the simplest of all fermentation systems and open vessels are easy to clean, but before the days of vacuum scavengers and the like, it was difficult to physically skim the yeast from the surface of a brew. The yeast could not be removed thoroughly, there was always some yeast remaining, and at feast some of this dropped into the beer. Furthermore, in a very large brewery containing many fermenting vessels, a whole army of men would need to be employed simply skimming yeast all day. It was not long before some bright spark realised that, rather than try to remove the yeast from the beer, it would be far easier to remove the beer from the yeast; and thus the dropping system was born.
Fermentation is started in a primary vessel situated at the top of the brewery. After the beer has been fermenting from twenty-four to thirty-six hours, or when it has attenuated to about half gravity, it is "dropped" - allowed to run by gravity into another vessel situated on the floor below.
Transferring the beer to another vessel not only leaves the dirty primary yeast head behind, but also racks the beer off the sediment on the bottom of the primary vessel. Trub, dead yeast cells, flocculum, and other undesirable matter is left behind. The wort gets thoroughly roused and a new protective yeast head is soon formed.
Fermentation is completed in this second vessel, whereupon the ale is dropped into the racking tank situated on the floor below. Here it is allowed to stand for twelve to eighteen hours in order to allow more debris to settle out, at which point the casks are filled.
Almost every commercial brewing book, from Levesque's in 1856 through to Jefferies' in 1956, states quite pedantically that ales produced by the dropping system are far superior to those produced by other methods. It is true to say that beer from breweries that practised the method were usually highly regarded. All of the world famous British pale ale breweries used the dropping system. Bass, Ailsopp, Flowers, Joules, Simmonds, Walker, and many others used variations of the dropping system. Morlands of Abingdon, and Marstons of Burton, are two of the few remaining brewers that still use the system. It is not considered to be economical as regards space and vessel utilisation and is slowly becoming extinct.
The patent Union cleansing system
This is the most famous fermentation system of all and incorporates the best of both the cleansing system and the dropping system. It is usually referred to as the Burton Union System because Burtonians like to believe they thought of it first, but in fact they had nothing to do with it. The automatic, self-filling, cleansing unions were patented in 1838 by Peter Walker, a Scotsman and Liverpool brewer.
The union system is a development of the puncheon system described above, except that the trough is mounted above the casks, rather than below them. Each union is a series of about six-teen casks arranged in two rows back to back. A long, swan-neck pipe rises vertically out of the bung hole of each cask and commands the trough. The trough known as the balm trough, is sit-uated above and between the two rows of casks. The gas generated by fermentation causes the yeast to be forced up the swan neck pipe, which then discharges the yeast into the trough. The wort forced up with the yeast runs back into the casks via a union pipe which connectes the balm trough and all the casks together via the lower hole in the cask, hence the term union. The yeast remains behind in the trough from where it can be collected. At the end of fermentation the yeast is in the trough, leaving comparatively clear beer in the casks. The system behaves in the same way as the simple cleansing cask system, except that the casks are topped up automat-ically, and therefore do not require someone in attendance twenty-four hours a day.
Fermentation is started in a conventional open fermentor, but when the beer has been fermenting for about thirty-six hours it is dropped into the unions situated on the floor below and fermentation is completed in these. At the end of fermentation the beer is run from the unions into the racking tank, where it is allowed to stand for about twelve hours before casking. The union system produces beer of a flavour much esteemed by devotees of Burton beer. The yeast recovered from the unions is particularly vigorous and was much sought after as pitching yeast. The large pale ale breweries of Burton upon Trent were enthusiastic users of the union system and hence it is commonly known as the Burton union system, but patent cleansing unions were in use by breweries all over the country. Even Watney's of Mortlake had some. I suspect that the union system of brewing was as much responsible for the fame of Burton-brewed beers as was any other factor. At the turn of the century the various union rooms at the Bass brewery contained a total of 4,590 union casks, each containing 144 gallons. Alas, due to the high cost of maintenance, the system is almost extinct. Bass stopped using their unions in 1983. Only Marston's Pedigree is still brewed using the union method.
Yorkshire stone square
This technique evolved to cope with a particularly flocculant type of yeast favoured in Yorkshire and the north. This yeast readily separates from the beer; so readily, in fact, that it does not stay in the beer long enough to produce much alcohol. It needs to be roused frequently, that is stirred into the beer. Furthermore, some of these yeasts cannot maintain anaerobic conditions for long periods and need to be frequently aerated. The aeration causes copious amounts of surplus yeast to be generated which has to be frequently removed. The Yorkshire breweries tolerate such a troublesome yeast because it produces beers that drink very full for their gravity and produces a rough sweetness on the palate.
A special fermenting vessel evolved to cope with this yeast. The fermenting vessel consists of two chambers; an upper and lower chamber connected by a manhole or vent through which the yeast can rise. Fermentation is started in the lower chamber, and the yeast rises through the manhole and into the upper chamber, known as the barm deck or yeast deck. About every two hours beer from the bottom chamber is pumped into the yeast deck via a fishtail spray. The spray discharges above the yeast head, aerating the wort, and mixing yeast in with the beer. The yeast and beer is allowed to run back to the bottom of the lower chamber via a return pipe. Yeast can be collected from the yeast deck as necessary. When fermentation is complete, the yeast is collected and the lower chamber is sealed by closing down the manhole. The beer is then left in this state for two days before being racked into casks.
The Yorkshire stone square was traditionally made from stone or slate. The high thermal inertia and coolness of these materials helped to check the rise in temperature during fermenta tion Modern ones are made of stainless steel with cooling apparatus fitted. In the old days, the pumping from the bottom chamber to the yeast deck was performed by manual forcing pumps, requiring the attendance of an operative twenty-four hours a day. The modern variety are electric and automatic
Conical fermenter
The modern fermentation system is the conical fermenter. These are fully enclosed cylindro-conical vessels which can be as large as fifty feet high and twenty feet in diameter, holding as much as 100,000 gallons. The base of this type of vessel is cone shaped, hence its name. Due to their size they are usually sited outside the brewery in the open air and are therefore well insulated from the effects of the weather.
Due to the high hydrostatic pressures generated by their height, these vessels maintain very high concentrations of yeast and are able to ferment a typical beer in less than forty-eight hours.
The vessels are fitted with cooling jackets to control fermentation temperature, the cone shaped base having its own separate cooling system. When fermentation is complete the temperature of the beer is lowered. This causes the yeast to sediment into the cone which is maintained at a lower temperature than the rest of the vessel by the separate cone cooler. The sedi-mented yeast packs down firmly into the cone, and can then be easily drawn off from the base of the vessel with minimal beer loss.
Maturation and barrelling
The beer is eventually transferred from the fermentation vessel into a racking tank. Here primings are added if required, and the beer is allowed a time to settle before being carefully syphoned into the barrels. A small quantity of hops is often added to the barrel to give the beer extra flavour and aroma, a technique known as dry hopping. The beer is then placed into storage to mature. Maturation can take anything from about ten days for an ordinary bitter, to several months for an old ale. Just before delivery to the pub a quantity of isinglass finings are usually added to the barrel to assist in clearing the beer after arrival at the pub.
In the pub
On arrival at the pub the beer can be stored shive upwards until a couple of days before it is needed, at which time it is carefully placed on to the stillage, vented and tapped. It is then left a couple of days in order to allow the secondary fermentation to subside and for the beer to settle. Venting is accomplished by replacing a hard peg with a porous one, thereby allowing excess gas to escape. Once the secondary fermentation has subsided or "gone quiet" and it has "fallen bright" it is ready to be served. The soft spile is replaced by a hard spile if the beer is in danger of going flat.
The temperature at which the beer is stored and served is obviously important. The ideal tem-perature is between 12°C and 15°C. The deep cellar of a traditional pub keeps a fairly constant rnperature throughout the year, but problems are often experienced in high summer. In days now almost past, the publicans would keep their beer cool by covering the barrels with wet hop sacks, but many modern pubs are equipped with air conditioned cellars.
Read also: