Difference between revisions of "German Brewing between 1850 and 1900: Fermentation and Beer"

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(Fermentation)
(Fermentation)
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Top yeast causes top fermentation and bottom yeast causes bottom fermentation. But with the right temperature the type of the yeast can be changed. If one takes the yeast rich foam of a top fermentation and adds it to wort and lets this stand at a temperature of 5C then the yeast is doing a bottom fermentation. Only little rises to the top. If one uses this yeast for fermenting fresh wort at low temperatures again then the former top yeast will completely transform into bottom yeast. Likewise can one create top fermentation and top yeas from bottom yeast by fermentation at 15 or more degrees C. ''This is an interesting observation. We know now that ale yeast is not going to change into lager yeas just based on the temperature but what may have happened is that the yeast that was used was not a pure ale or lager strain. It was a mix of strains and fermentation at lower temperatures benefited the lager type cells and fermentation at higher temperatures benefited the ale type cells.''
 
Top yeast causes top fermentation and bottom yeast causes bottom fermentation. But with the right temperature the type of the yeast can be changed. If one takes the yeast rich foam of a top fermentation and adds it to wort and lets this stand at a temperature of 5C then the yeast is doing a bottom fermentation. Only little rises to the top. If one uses this yeast for fermenting fresh wort at low temperatures again then the former top yeast will completely transform into bottom yeast. Likewise can one create top fermentation and top yeas from bottom yeast by fermentation at 15 or more degrees C. ''This is an interesting observation. We know now that ale yeast is not going to change into lager yeas just based on the temperature but what may have happened is that the yeast that was used was not a pure ale or lager strain. It was a mix of strains and fermentation at lower temperatures benefited the lager type cells and fermentation at higher temperatures benefited the ale type cells.''
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Light beers, which aren't expected to last a long time, are fermented with top yeast. It finishes the fermentation quickly, converts lots of the sugar in alcohol and produces lots of carbon dioxide (the reason for the strong foaming of the ''Weissbiere''). But because the fermentation is done at higher temperatures they tend to get sour very easily and the protein is not precipticated as completely. Such beers are not stable and need to be consumed quickly.
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For beers whose small amount of sugar should not ferment completely, like the Bavarian and other lager beers, a the bottom fermentation is chosen. In this case the process is a slow one and the beers can be consumed months after being brewed. The protein settles out with the yeast and during their shelf life these beers will get better with every day.
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For top and bottom the process of fermentation is divided into three different phases. During the first, which starts after the addition of the yeast, sugar is converted into alcohol and new yeast is formed from the nitrogen compounds. The temperature of the fermenting substance rises. This part is called the rapid or wild fermentation.
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The second phase is the secondary fermentation (''Nachgaerung''). And while the conversion of the sugar still continues it is much slower and most of the yeas formed during the first phase settles out. The turbid beer clears up. The third phase is called the impalpable. It happens after the settling of the yeast and clarification. If that was complete the continued fermentation and yeast growth is so slow that there is still the fermentation of sugar and formation of carbon dioxide but the settling of the yeast is so slight that it is a mere haze on the side of the bottle on which it was laying. A haze that the maid pretends not being able to remove but which needs to be removed if one doesn't want to drink sour beer as it would immediately start the second stage of fermentation in the beer that is filled into that bottle next. ''Second fermentation means in this context the souring of the beer as this as seen as yet another fermentation stage that happens to the beer.''
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==The bottom fermentation==

Revision as of 06:06, 24 February 2009

This second article about German Brewing in the later half of the 19th century covers the fermentation process and select beer styles as outlined in "Chemie fuer Laien" (1860). The first article (German Brewing between 1850 and 1900 : Malting and Wort Production) covered the brewing process from steeping the malt to cooling the wort.

Fermentation

The production of a good beer depends very much on the chemical process which we call fermentation. As a result the brewer has to give it his utmost attention. If it runs badly the beer will be bad even if all other processes ran well and were controlled with care. But if it runs well it is possible to compensate for small mistakes made up to this point. Except if the wort got sour because in this case the 2nd fermentation already happened before the 1st one started.

The beer fermentation is divided into two groups: top fermentation and bottom fermentation. Both types convert the sugar into alcohol and carbonic acid. But in beer this conversion should not be run until completion because one would like to have not only alcohol but also substance in the beer. The alcohol makes the beer invigorating, the carbonic acid gives it the refreshing taste, the unconverted sugar makes it nutritious and the hops give it the spice. The fermentation should not destroy these properties nor should it affect them negatively and thats why it is so important to control it well. Today we know that there are fermentable and unfermentable carbohydrates in the wort and that the yeast can consume only the fermentable ones anyway

Besides the mentioned primary purpose should the fermentation facilitate the precipitation of a substantial amount of the protein. The more it is removed the more stable the beer will be. But the beer should never become void of any fermentation substrate, because unlike vine it is not a fully fermented beverage. If it would become that it would stop being pleasantly drinkable. The carbon dioxide, which is formed through fermentation, is substantial condition for the pleasant taste. It is not present in vine since there the fermentation is complete and all the carbon dioxide has escaped. It sounds as if the author was not aware that carbon dioxide is trapped in the beer if the vessel is closed and that it can retain carbonation even after complete fermentation. To prevent such a staling of the beer the beer needs to retain enough fermentation substrate such that it can slowly ferment throughout its existence. This is the same with Champagne.

The temperature has a major effect on the course of the fermentation. At a temperature of 15 or more degrees (C) is the fermentation turbulent, quick and very active. At 7 C or less the fermentation is quiet and much slower. The yeas rises to the top during the faster fermentation at higher temperatures. The carbon dioxide bubbles lift the yeast to the top this is why this process is called top fermentation (Obergaerung). At lower temperatures less carbon dioxide is produced and the bubbles are too small to carry anything else but themselves and the yeast falls to the bottom. This is why this process is called bottom fermentation (Untergaerung).

Top yeast causes top fermentation and bottom yeast causes bottom fermentation. But with the right temperature the type of the yeast can be changed. If one takes the yeast rich foam of a top fermentation and adds it to wort and lets this stand at a temperature of 5C then the yeast is doing a bottom fermentation. Only little rises to the top. If one uses this yeast for fermenting fresh wort at low temperatures again then the former top yeast will completely transform into bottom yeast. Likewise can one create top fermentation and top yeas from bottom yeast by fermentation at 15 or more degrees C. This is an interesting observation. We know now that ale yeast is not going to change into lager yeas just based on the temperature but what may have happened is that the yeast that was used was not a pure ale or lager strain. It was a mix of strains and fermentation at lower temperatures benefited the lager type cells and fermentation at higher temperatures benefited the ale type cells.

Light beers, which aren't expected to last a long time, are fermented with top yeast. It finishes the fermentation quickly, converts lots of the sugar in alcohol and produces lots of carbon dioxide (the reason for the strong foaming of the Weissbiere). But because the fermentation is done at higher temperatures they tend to get sour very easily and the protein is not precipticated as completely. Such beers are not stable and need to be consumed quickly.

For beers whose small amount of sugar should not ferment completely, like the Bavarian and other lager beers, a the bottom fermentation is chosen. In this case the process is a slow one and the beers can be consumed months after being brewed. The protein settles out with the yeast and during their shelf life these beers will get better with every day.

For top and bottom the process of fermentation is divided into three different phases. During the first, which starts after the addition of the yeast, sugar is converted into alcohol and new yeast is formed from the nitrogen compounds. The temperature of the fermenting substance rises. This part is called the rapid or wild fermentation.

The second phase is the secondary fermentation (Nachgaerung). And while the conversion of the sugar still continues it is much slower and most of the yeas formed during the first phase settles out. The turbid beer clears up. The third phase is called the impalpable. It happens after the settling of the yeast and clarification. If that was complete the continued fermentation and yeast growth is so slow that there is still the fermentation of sugar and formation of carbon dioxide but the settling of the yeast is so slight that it is a mere haze on the side of the bottle on which it was laying. A haze that the maid pretends not being able to remove but which needs to be removed if one doesn't want to drink sour beer as it would immediately start the second stage of fermentation in the beer that is filled into that bottle next. Second fermentation means in this context the souring of the beer as this as seen as yet another fermentation stage that happens to the beer.

The bottom fermentation