Difference between revisions of "German Brewing between 1850 and 1900 : Malting and Wort Production"

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Whether the wort has been produced using the English method or the one in which the mash is boiled boiling the wort is cannot be skipped. There are always 2 reasons that require the boiling. For one is the wort never produced strong enough that it can be left without removing part of the water through boiling and secondly contains the wort proteins that need to be coagulated through boiling which lets them settle to the bottom and helps with clearing the beer.

Revision as of 00:13, 15 February 2009

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This article tries to shed some light on the German brewing practice that as it was practiced in the later half of the 19th century. It is largely based on the description of the brewing process as it is found in various books of that time. In particular the Brockhaus Konversations Lexikon (conversation encyclopedia) of 1898 and the book "Chemie fuer Laien" (layman chemistry). Althogh neither of them are brewing textbooks as they were targeted at the curious and affluent part of the public their description of the brewing process is surprisingly detailed and can only be covered in excerpts here. The actual details of the brewing practice of a particular brewery was a well guarded secret that was passed on from generation to generation and rarely published in textbooks. Brewers back than had only a limited knowledge of the science behind brewing and once they found a way that worked they made sure that a competing brewery would not benefit from that knowledge. Most of the pictures were taken in the Bavarian Brewing Museum in Kulmbach (Germany).

The following outline of the brewing process is largely taken from the book "Chemie fuer Laien" (layman chemistry) which was published in 1860. Occasionally I'll add comments which will be set in italic. Native German brewing vocabulary will also be set in italic and a fitting translation may be provided in parenthesis. While this book was published in the Prussian part of Germany it does make references to the Bavarian style of brewing:

The brewing process consists of 3 main parts: malting, wort production and fermentation. Only 3 ingredients are used in brewing: water, malt and hops. Luis Pasteur discovered yeast in the late 1860s, which means that this book was written without the knowledge of yeast. Some other books from the same time refer to the yeast as "ferment" and the addition of "ferment" to the wort At this time many brew masters even strongly believed that only barley can be used in brewing and "that every one who says something else is a fool and who actually believes it is an even bigger fool". But in fact wheat and occasionally oat and rye were malted and could be used as well.

Malting

Malting is nothing more than the germination of the grain and its interruption at the right time. Finding "the right time" is the sign of a skilled brew master. And now that we have the thermometer it has become child's play compared to past times where the bare hand was used to measure the temperature At this time malting was not as separated from brewing as it is today and most breweries would include malting facilities in which the malt for the beer was produced.

Steeping

Malting itself consists of three steps: steeping, germination and kilning. For the first step a wooden or stony vessel of a size that matches the needs of the brewery is used. This is the Quellbottich or Malzstein (steeping tun, malt stone or just steep). It's better to make it of stone than of wood as stone vessels are nearly indestructible and don't give off any flavors to the malt. The Malzstein is filled to its half with clean and soft river water and the grain is added. It's important that this malt comes from a single source. Otherwise they may behave quite differently in the Quellbottich. Back then they already realized that the growing conditions of the malt have a significant effect on the speed in which it germinated. If a mix was used some of the malt may become overmodified while the other part is undermodified.

After the grains have been added to the water such that the water stands about 6 inches above it, it is well stirred with paddles. Blind grains will immediately rise to the surface which have to be removed since they are not able to germinate and would give the resulting beer a bad taste. It takes about 6 hours to remove everything from the grain which hasn't much uses except for chicken feed. While this is done the water becomes very cloudy and has to be replaced. This has to happen every 12 hours in the summer and ever 24 hours in the winter. Once the water runs clear and colorless the changing of the water stops.

Young and fresh barley malted in the summer takes about 2 to 2 1/2 days until it is fully swollen. Old barley takes up to 4 days in the summer and may take up to 6 and more days in the winter when the temperature is barely above 8C (46F).

But this process of steeping in tuns leads to the loss of protein and sugar (The author wrote actually rubber and sugar. I think that rubber refers to the protein content of the barley) which is why the Bavarian style of malting only steeps the grain until all the blind kernels have been removed and dirt and dust have been removed. Then the water is drained and the malt is shoveled onto the Malztenne (malting floor or just floor) and left to dry on the surface of the pile. After that it is moistened with a watering can and turned. The amount of water is just enough such that none of it runs off the grain onto the floor. All that water will be taken up by the grain and it swells fully.

The test if the malt has fully swollen is done by holding one tip of the grain between thumb and index finger and squeezing it together. If the other end breaks open and the contents of the grain is pushed out it has reached the desired state.


Germination

Germination is what follows the steep. It happens on the Malztenne which has a floor that has an even floor without gaps and holes in which grains could hide or the shovel could get caught at (see here for a picture of such a Tenne from the Weyermann malting company). Its size is such that about 3 square feet floor are available for each shovel of grain. The malt is brought onto the Tenne in a rectangular pile that stands about 6 inches high and is left as is until the top doesn't feel wet anymore and the tip of the grains show a little white which is the start of the germination. Now the grain is brought to the actual germination and for that is shoveled into a pile that stands about 2 feet high in the winter and about 1 1/2 feet in the summer. The actual height depends on the temperatur of the Tenne the higher it is the lower the piles will be. It is desirable to have an internal temperature of the grain piles of about 12 to 15C. This requires larger piles in the winter and lower ones and increased ventilation in the summer. The best seasons for malting are spring and fall as the ambient temperatures are optimal and it is suggested that a brewery should malt all the malt needed during these seasons.

The pile now starts to sweat and emits an apple like aroma. At this stage the thermometer shows a temperature of 5 to 8 C above ambient and if the pile is left as is the germination would proceed with immense speed. As soon as the rootlets become visible the malt pile is spread out to slow down the germination. In this process the wet and warm grain from the center of the pile is moved outward covering the grain that has so far been on the outside. This cools down the grain from the center and warms the grain from the outer regions. The pile is then left as is until further signs of rootlet growth are visible after which the process of turning the malt is repeated. This is continued until the rootlets are as long as the grain (in case of wheat) or about one quarter longer (in case of barley). When the desired length of the rootlets is reached the germination process is interrupted by spreading the malt on the Malztenne which prevents a further warming.

This process takes about 14 days. In order for the germination to be even among the malt the brew master has to pay close attention to the temperature of the malt pile. It should never exceed 25C and that only when the pile is still tall. The highest temperature tends to occur 4 days after the malt has left the steep.

The goal of malting is to convert as much of the flour in the grain to sugar which is what the germination process accomplished. Obviously this is not completely true as we know now. Malting is for the development of enzymes and cytolosis which is the degradation of the cell wall structure in the endosperm.

During the germination sugar is formed but only as much as the sprouting germ needs. But the brewer wants to convert the complete starch content to sugar before the sprout uses it all. Which is why he lets the conversion process start but interrupts it as soon as he thinks that the spout is consuming it.

The views of different brewers about one or the other aspect of steeping and germination are widely different. For example Bavarian brewers prefer the method of steeping on the Tenne through sprinkling with water while others completely reject this method. Some say that if the upper layer of malt dries out during the germination process it is ok to sprinkle warm water onto the pile while others believe that this should never been done because of its detrimental effect on the beer quality and that it is better to cover the drier malt with more moist malt. Back then brewing science has not evolved yet and brewers knew to stick with what has worked for them in the past. Another example involves the length of the germination process. Some prefer a longer germination because it results in good looking bright beers while others prefer a shorter germination because it results in more robust tasting beers. But most likely the length of the Germination process has no effect and it depends on the type of grain that is used. Now we know that the length of the germination process does affect the clarity of the beer. Longer germination leads to higher modified malts which contain less haze forming protein. But such malts are also known to produce thinner and less robust tasting beers.

The transformation of grain into malt causes the transformation of starch into sugar. This is brought on by a peculiar compound that is present in the germination point of each of these grains. The french chemists Payen and Persoz discovered this compound and called it Diastas from the greek word Diastatsis which means expansion or splitting of matter. This Diastas is contained in a much larger amount in malt than what is needed to convert its starch into sugar and can therefore be used to convert an additional amount of non malted grain. This is where we get the word diastatic power from. Back then they know that there is something in malt that converts the starches and they knew how to get it but they didn't know about the various enzymes that make up the Diastas.

Drying and Kilning

The drying of the malt happens on the Schwelkboden or Welkboden (lit. wilting attic). This is a well ventilated room about five to six times the size of the Malztenne. The malt is spread on its floor to stand at most 1 1/2 inches high. It is left there for it to cool and loose its moisture. It's meant to dry and to wilt. For this purpose the room has ventilation openings that are close to the floor such that the air can easily flow across the layer of malt. The malt is turned six to eight times per day and the dried malt is called Luftmalz (air malt). 100 pound barley yield about 92 pound Luftmalz. 2 to 3 pound are lost during steeping, 1 1/2 to 2 pound are lost during the germination process and the rest are rootlets that broke off when the malt was germinating on the Tenne'.

But only rarely is malt used it is air dried form. Generally it is artificially dried in the so called Darre (kiln) which is a device that allows the removal of additional moisture through increased temperatures. It is commonly thought that the purpose of the Darre is to give the malt a desired level of dark color. But if malt is roasted so dark that the color of the beer is colored then the malt would be lost. The length of the boil and the associated transformation of sugar into caramel is what gives the beer its color. This is an interesting statement. Not only does the author think that kilning malt too strongly would waste it but he also makes a reference that it was common practice to control the beer color though the length of the boil. Now we know that the kilning temperature used has a significant effect on the character of the beer and that this way of controlling the beer color is better than extremely long boils

Figure 1 - (A) a schematic drawing of a simple Darre with only one grate. This particular kiln design is direct fired. (B) A more complex triple grate kiln design. Note the teardrop shaped cross sections of the heating ducts below the lowest grate. These ducts would carry the hot exhaust fumes from an external furnace (it could be the furnace for the brewhouse or for the brewerie's steam engine) and heat the air. (C) A typical design for the hood of a kiln. This hood is able to rotate and the weather vane on its top will make sure that the opening is always away from the wind. This keeps the wind from blowing the moist air back into the kiln. (D) cross sections of various heating duct designs. Note that they all have a tip and slanted sides on the top. This is to prevent malt grains from laying on the heating duct and being subsequently burned. (E) a sample layout if of the heating ducts


Figure 2 - An old malting building in Bayreuth Germany showing a rotating hood


The Darre is a large metal mesh generally suspended halfway up in a dedicated building such that it is accessible from all sides. The mesh allows for the hot air to rise through the grain but prevents the grains from falling through. Figure 1-A shows a simple direct fired kiln. The fire burns in the bottom of that kiln and the hot combustion gases rise through the grain and then through a flue to the outside. Vents on the side of the furnace allow the control of cold air that mixes with the exhaust gases and which allows for a crude temperature control. The problem with kilns like these is that the wood needs to burn very cleanly which is never the case and the malt gets a smoky and sometimes burnt character.

The flue has top be large enough to allow for the water vapor to escape unrestricted. At the top of the flue sits a rotating hood (Figure 1C) with an opening that is always turned away from the wind in order to prevent the wind from blowing the water vapor back into the kiln.

3 different types of kilns exist. Rauchdarren (smoke kilns), Luftdarren (air kilns) and Dampfdarren (steam kilns). Smoke kilns are these for which one does not start a dedicated fire but they are fueled by the smoke from brew kettle or steam engine furnace. This allows for an more efficient use of the wood or coal used by the brewery. Luftdarren (air kilns) have an iron furnace that heats the air used for kilning the malt. Dampfdarren (steam kilns) are similar to smoke kilns as they use ducts in which hot steam flows and then heats the air within the kiln.

The tubes used to carry steam or smoke are not round but have a triangular crossection with the tip directed upward. This is intentional because some of the maly kernels tend to fall through the mesh and if they land and remain on the hot tubes they would get burnt and impart that burnt aroma onto the malt in the kiln. Figure 1D shows some typical cross sections. It is also important to seal the joints of the tubes in order to prevent the smoke or steam from entering the kiln.

A common improvement these days is the addition of additional grates above each other in the kiln. Malt enters the kiln on the top grate and exists after it has been fully kilned on the lowest grate. The idea is that the air that comes from the lower grates is not saturated with moisture yet and can still remove some moisture from the more moist malt on the upper grates.

The size of the kiln depends on the size of the brewery. With simple single grate kilns with an area of about 100 square feet can kiln about 400 pounds of malt each day. Drying and kilning 100 pounds of malt takes about 25 pound of dry wood. And according to Stohmann and Bailling 100 pound of barley yield about 92 pound Luftmalz and 80 pound Darrmalz (kilned malt).

While malt is dried in ambient air no chemical changes happen. It just loses water. The drying in the kiln has besides removing the moisture another goal. The from the gluten formed Diastas should react with the starch in the grain more strongly. And it is without question if this statement is correct as Luftmalz gives much less sugar its extract than the same amount of Darrmmalz. This is yet another statement which is confusion to us modern brewer. First off the kilning process, at least for base malt, is not supposed to activate the enzymes and create more sugar and secondly air dried malt should give more sugar in mashing since it has the highest dizatatic power as the enzymes have not been damaged through kilning. If the malt is not fully dried before the heat in the kiln is turned up the enzymes are severely damaged because of the presence of water. The latter is the case in the production of crystal malt. Aside from this the roasting also gives the malt the pleasant aromatic taste, the roast aroma, which improves its taste and stability.

The temperature has a multitude of effects on the beer. The higher it is to some extend the more starch "rubber" is formed. If this temperature is exceeded much of the sugar is converted into caramel and the beer looses much of its strength. The author talks about the starch being broken down into rubber and sugars. Since there is no actual rubber in the malt extract I assume that he means dextrins with this. In fact higher kilned malts do produce more dextrines and less sugar but only because they have a lower beta amylase content. But he may also be talking about the preparation of crystal malt. But that would mean that back then the beers used crystal malt as base malt wich doesn't match earlier statements which mentioned that the malt is easily breaks apart when rubbed between the fingers.

Figure 3 - comparative analysis between barley and malt from Meyers Konversationslexikon, 1893. Top row: 100kg dry barley, 88.81 dry malt, difference. Left hand column: Starch, protein, dextrin, sugar, oil, fiber, ash, total. Note that the starch content was much lower than that of modern barley and that the protein content was much higher.

Earlier the bavarian breweries would rarely kiln their malts above 50 to 60 deg R (63 - 75 C). But this has been abandoned and now the malt is kilned at up to 80 deg R (100 C) and some breweries even go up to 100 deg R (125 C). Believed that the malt would loose its sugar forming power if kilned too hot. But this only happens if the malt enters the kiln wet and is heated like that. But when heated dry the malt doesn't loose this power but at 80-90 deg R (100-112C) more Roestgummi (roast-dextrins) is formed compared to kilning at 50 to 60 deg R (63-75 C). This Roestgummi is what makes the beer fuller and more nutritious. It dissolves in the wort like the sugars. The latter is converted to carbonic acid and alcohol during fermentation but that doesn't happen with the Gummi. It remains and makes the beer nutritious and heavier than water. This is yet another indication that the ominous mentioning of "Gummi" refers to dextrins and not to actual rubber. Regarding the temperature of the kilning, we now know that highly kilned malts produce more dextrin rich worts not because that dextrin is formed during kilning but because more of the fermentable sugar producing beta amylase is destroyed. This statement was also interesting in another aspect. It is commonly believed that Bavarian brewers (or at least the ones in Munich) used to kiln their malts high and then started to change the process to create lighter beers with lower kilned malts but the opposite was mentioned here

The malt is considered done once the rootlets easily come of when the malt is rubbed in the hand and the peculiar malt aroma has developed. And finally the color that the brewer desires is reached. Good malt should have the known and pleasant yet peculiar smell and should be so light that it floats in water. Some breweries may take a part of the malt and roast it completely brown. The resulting malt is called Farbmalz (colored malt) and used to give the beer a nice dark color. The process of making it is simple. It is placed into large drums and roasted like coffee beans.

Wort production

Mashing is separated into 4 different sections: Milling of the malt, dough-in, boiling of the wort and the chilling of the wort. It appears that the author considers the complete hot side of the brewing process as mashing

Malt milling

Figure 3 - Drawing of a malt mill (from Meyers Konversations-lexikon, 1893). The malt enters through the funnel a and hits a rotating prism b. From there it falls into the enclosed space e and onto the rollers f and g. g is fixed while f is movable and pressed against g through the lever l and the counter weight i. The scrapers k and k are pressed against the rollers and remove grains that stick to the rollers. The crushed malt falls down the chute m into a bin

To grind the malt one uses the common mill only reluctantly as it crushes the malt too finely for it not to be dissolved in water and form a paste from which one tries in vain to produce a clear beer. But some places have a malt tax and brewers are not allowed to own their own mills. But where it is necessary to use the common mill the deficiencies of grinding in them are counteracted by wetting the malt. Generally water of 1/8 of the malts weight is added and the malt is well distributed by shoveling the malt from all sides of the pile. After a rest of 12-18 hours the malt is brought to the mill where it is ground with a wider than usual gap between the millstones.

One is better off of if one can use the own mill. In this case the mill consists of two cast iron rollers between which the malt is crushed. They are operated by two day laborers or a steam engine. Malt that is crushed with such mills doesn't need to be wetted but it still needs to be ridded of dust and other uncleanliness as they would impede a foul taste on the beer.

Many brewers use cats to control the destruction brought on by mice in the malt storage. While the cats don't eat malt they have the bad habit that cannot be broken. They never leave their droppings on the open floor but always bury it in the malt. While the dry matter is easily removed through sieving later it is the wet excrements that that penetrate the malt and give a disgusting taste and aroma that can be found in the beer. I found it interesting that the author dedicated a full two paragraphs to elaborate on the problem with cats and their excrements which means that this was a real problem back then.

Water

It is beyond words how indifferent most brewers are towards the water. There are so many salts and minerals in water which looks so clear and color less. But just look at the boiler of a steam engine in which the lime scale can be many inches thick.

Now are these brewers, who are indifferent to their water, correct if they say that these salts and minerals will be precipitated and removed though the boiling, fermentation and the salts and acids in the beer. But they also admit that this process consumes not unimportant compounds from the beer, some of which are necessary for the pleasant taste and stability of the beer. And that more of them would be retained in the beer if they wouldn't have to clean the water. It seems that back then there was very little understanding of the importance and acceptable ranges of minerals in the brewing water.

The author goes on to mention that soft water is the best water for brewing but that in cities like Munich, where the water is so hard that the chalk encrusts the rocks in the river Isar, brewers make some of the best beers. He also mentions Buton ales and the very hard water that they are made with. All in all there is no conclusion why that is.


Brewhouse technology

Figure 5 - Schematic drawing of a small mash tun from Meyers Konversationslexikon of 1893
Figure 6 - The mash tun (left) and boil kettle (right) of a small brewery as it is on display in the Bavarian Brewing Museum in Kulmbach Germany

The main vessel in mashing is the mash tun. Its size depends on the size of the brewery but it has to be designed such that it holds twice as much volume as the beer that should be brewed.

The following description of brewhouse technology in the 2nd half of the 19th century has been pieced together from different sources.

Small breweries would consist of 2 vessels. One for mashing and lautering and another for boiling the mash and wort. Only the latter had the ability to be heated. The heat would come either from a coal or wood fire that was located under that kettle. Figure 6 shows a picture of such a mash/lauet tun as well as the boil kettle. The mash tun would be made from either iron or wood. Wood was able to better retain the heat of the mash while ion is more durable and more easily maintained. Figure 5 shows the cross section through such a mash tun. The shaft a in the middle propels 2 titled blades b close to the bottom of the tun. Their purpose is to keep the mash from settling and generate a rotation motion. The vertical bars c would then create turbulences that mixes the mash. The mash tun also contains a perforated false bottom which allows it's use as a lauter tun. This false bottom sits 2-4 inches above the actual bottom and may be made of wood or iron with iron being more popular. Between the false and the true bottom is a valve that allows the wort to be drained. In larger designs multiple valves may exist each of which is connected to a different section though pipes.

Figure 7 - Schematic drawing of a more modern and more mechanized brewhouse. Taken from Brockhaus' Konversations-lexikon of 1898.
Figure 8 - Simple 2 vessel brewhouse in the Bavarian Brewing Museum in Kulmbach, Germany

Note the malt mill on the top floor, the grist case on the floor below and the chute through which the malt falls into the mash tun. The lower right shows the boil kettle which is mostly encased with a brick structure that also houses the furnace which provides the heat. This type of brew house also uses a pump to pump the mash from the kettle back into the mash tun. Figure 8 shows almost the exact same brew house rebuild in the Bavarian Brewing Museum.

Figure 9 -

Mashing

Once we have good malt and the best possible water we can continue to dough-in. Its purpose is to dissolve the soluble compounds of the malt (sugar, dextrins and Diastas) as well as the yet unconverted starch. If possible the spent grain should not contain any soluble compounds. But this is a godly wish which is far from being granted.

Not only does mashing dissolve compounds from the malt it is also a chemical process which converts the still present starch into dextrins and sugar. The sugar is giving the beer it spirit and the dextrins are giving it is nutritiousness.

In England where a very strong beer is brewed the brewer uses about 180 pounds of water for each 100 pounds of malt where as, without a doubt, German brewers are using much more otherwise the beers wouldn't be as thin. They are using 750 to 800 pounds of water for each 100 pounds of malt.

The author asked a brewer in Stuttgart whom he has known for a long time how much malt he is using for a particular amount of water. "Nobody ever heard that from my mouth and even though you are not a brewer I will not make an exception", was the answer. If even this simple ratio is such a secret how much more secretive brewers are with respect to the time, temperature and other conditions. They are stubborn in their reticence as much as they are stubborn in sticking to their methods which they consider their own even though in some cases it is obvious that they have to be called inappropriate.

This statement clearly shows how difficult it is to get true insider information about brewing techniques and practices from that time. Unlike today there was no communication between the brewers and the idea of brewing schools or science didn't exist either. All the knowledge was handed down within the brewery

We will now look at the in Germany commonly used Thick-mash or Decoction-mash method. One half of the water is added to the malt already in the mash tun. While people mix this mash the other half of the water is brought to a boil in the boil kettle. This takes several hours (I was surprised by that) and only when the water and malt are completely mixed can the now hot water be added while the temperature of the mash rises to 35 C under constant stirring and mixing.

A significant part of this mash is scooped into the boil kettle and under constant stirring brought to a boil as quickly as possible. Based on the brewer the boil is continued for one half to one and a half hours. This is called the first thick mash boil.

After this is completed the boiling mash is brought back into the mash tun and under constant stirring the temperature rises to 45 to 50 C. Now another third of the mash is brought back into the brew kettle. (Note that the author doesn't mention a rest at this temperature. I assume that in this particular version of this mash the 2nd decoction is pulled as soon as the 1st one has been completely mixed in) This the the 2nd thick mash boil and after it is complete and returned to the mash the temperature rises to 60-65 C.

Another source indicates that the heating of the first decoction should take 40 - 45 minutes. This makes sense as a siginificant part of the conversion actually happens during the heating of the decoction especially since the decoction method described here doesn't hold a rest after the return of the 2nd decoction. A rest will be held later but only after the 3nd decoction which is a lauter decoction

After this the extract that has already formed is boiled. For this the liquid that has formed between the false bottom and the actual bottom is drained into the boil kettle as well as that which follows. This is called the lauter mash. It will also be boiled for a quarter to half hour and returned to the mash tun where it raises the temperature to 75C which is exactly the temperature at which the starch is converted into sugar. Some other authors report that temperature to be 65C.

I'm surprised that this worked the way he describes it. After 3 decoctions, one of which was a thin decoction, hardly any enzymes will be left. While a-amylase still works at 75C there shouldn't be enough left to convert all the starch. But as I pointed out earlier, most of the starch conversion must have happened during the heating time of the decoction. Looks like that the "other authors" that the author mentioned were closer to the desired rest temperature for the saccharification rest.

To give this process the necessary time the tun is carefully covered after the mash has been mixed well. 2 hours does this take. During this time the brew kettle as well as the lauter grant is cleaned. And now everything is drained that collects under the false bottom. This is done with the valve fully opened and the wort draws flour with it which has collected under the false bottom. The wort is again returned to the mash tun where it is mixed with the mash and what is now running though the perforated bottom runs pretty clear and is heated in the brew kettle. This is called the first wort and gives the actual main beer.

In some places is the drain closed after the run-off of the first wort and a 2nd quantity of boiling water is added the the spent grain which gives the so called Nachbier (after beer). It is understandable that after the first operation a non unsignificant amount of unconverted starch, coagulated protein and Diastas remains and that much of the good wort remains in the spend grain which act like a sponge. Most of this is dissolved with with this 2nd infusion. But the actual first wort is brought to a boil in the boil kettle. In some places the same is done with the Nachbier (this is what is commonly known as party gyle in English brewing and it looks as if this also existed in German brewing) while in others it is sold to the poor.

The here outlines method experiences not only where the Bavarian beer is brewed but also in Bavaria itself many changes. Because of which every place has its own beer and that even in large places like Munich beers are very different from each other.

Later the author also describes a technique where water is sprinkled onto the spent grain to "push out" the remaining first wort. This is essentially fly sparging.

There are 2 cliffs that need to be avoided in mashing: too little time for sugar formation and too much time for vinegar formation. If too little time is used the wort won't become sweet. But it it stands too long on the spent grain it will become sour. The use of Luftmalz (air malt) is more prone to give sour beers than the use of dark kilned malts. The dark malt formed roast dextrins, an essential oil, which protects against the souring of the mash. We now know that this is not what happens. The more highly kilned malts simply have less viable mash spoiling organisms on them because they have been subjected to a higher temperature. This is the reason why lager beers are not brewed in the summer. But top fermented beers which anyway are not expected to last for more than a few weeks. A slight sourness is part of the Leipziger Gose, the Berliner Weissbier and the Wiener Bluzerbier (this is the only reference I was able to find to a mysterious sour beer brewed in Vienna). But for Barvaian beers is such a level of sourness a major flaw that makes the beer undrinkable.

Boiling

Whether the wort has been produced using the English method or the one in which the mash is boiled boiling the wort is cannot be skipped. There are always 2 reasons that require the boiling. For one is the wort never produced strong enough that it can be left without removing part of the water through boiling and secondly contains the wort proteins that need to be coagulated through boiling which lets them settle to the bottom and helps with clearing the beer.