Revision as of 16:56, 8 February 2009

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 bang. 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

The Darre is a large metal mesh generally suspended halfway up in a dedicated building such that it is accessible from all sides.

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 such a rotating hood