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Robbie

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Here is an extract from a German technical brewing publication detailing the different approaches to Lager fermentation.

Lager_fermentation_charts.gif 

As you can see the Germans consider anything above about 9C to be a warm fermentation.

A) is a traditional cold fermentation and cold storage. Fermentation is complete in roughly 12-14 days and is allowed a further period at sub zero temps by which time diacetyl has dropped to levels that are imperceptible after about a month or so.

B) is the much warmer pressure ferment, where the temp is allowed to rise under pressure and we see a huge spike in diacetyl which is readily absorbed.  The pressure acts upon the yeast and slows down its metabolism much like cold does. Interestingly John Blichmann did an experiment between a traditional cold ferment and a pressure ferment and many preferred the traditional long ferment. Its in a Beersmith podcast somewhere.

C) is a cold ferment and then the temp is raised to around 12C when half the extract is still available.  It does result in a slight diacetyl spike but again this is readily absorbed.  This is the method that you find advocated by a lot of American brewers, a so called 50/50 ferment.  Cold fermented and then when 50% attenuation has been reached raise the temp the idea being that all the major characteristics are formed in the first few days of fermentation, or so the theory goes.

D) is similar to A, a traditional cold ferment for about 12-14 days then a controlled maturation by a gradual reduction in temp to sub zero lagering temps.  Appears to be sightly quicker than the traditional cold storage.

E) is a pressureless warm ferment, for the Germans that's 12C. Again we see quite a significant diacetyl spike which is readily absorbed by the time ferment is finishing out by about day 6-8. 

F) is a cold ferment and then leaving the Lager to reach room temp.  It results in the relatively small spike in diacetyl much like C above.

I thought it might be of some little interest to anyone experimenting with Lager brewing.


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Womble

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Oh Lord ... that's gonna have to wait, it's Friday ... week at work, my brain is in no state to deal with number crunching ...


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Chug

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I did the start cold and then increase to room temp after a week, I did the ferment and then raise to room temp, I did the minimum six weeks lagering, I did the double amount of yeast.

Now I just use the usual amount of yeast and just let it ferment at 10 - 12C then bottle and start trying from a week or so after they've carbed up, but they are best after a few weeks.
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Robbie

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Quote:
Originally Posted by Chug
I did the start cold and then increase to room temp after a week, I did the ferment and then raise to room temp, I did the minimum six weeks lagering, I did the double amount of yeast.

Now I just use the usual amount of yeast and just let it ferment at 10 - 12C then bottle and start trying from a week or so after they've carbed up, but they are best after a few weeks.


Its quite interesting, did you find very much of a difference?  From what I understand and from all the calculators Ive seen Lager is supposed to have about 350 billion cells for a 23L batch.  How they come to that figure I cannot say.  I read somewhere that its because of the lag time to prevent anything else catching a foothold in the wort prior to the yeast taking over.  With good sanitation i cant see how this is a problem. Personally I pitch fresh slurry if I can, about 350ml in a 23 liter batch. 

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Robbie

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Quote:
Originally Posted by Womble
Oh Lord ... that's gonna have to wait, it's Friday ... week at work, my brain is in no state to deal with number crunching ...



You said something on another thread that was very interesting.  You said that your lager had about 20% of adjuncts to take care of chill haze.  I have found myself that when I add wheat it is clearer than when I leave it out.  This is counter intuitive because wheat is supposed to have a greater protein content and thus more of a proclivity for haze causing qualities than barley, but on lagering it is clearer than pure barley.  I don't understand why, but it is.

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Pesho77

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 I just heard about that on a pod cast yesterday, it appears that whats happening it that things bind to the "larger" and therefore "heaver" particles in the higher protein adjuncts etc and then drop out quicker so leave a clearer beer.

 Pesh
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Robbie

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Reply with quote  #7 
wow amazing. Thanks Pesho I really wondered about it.
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Womble

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Reply with quote  #8 
I didn't know that ...

When I have used wheat flour in ales in the past it has thrown a haze, pearly white, quite pretty.

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Womble

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Okay ... number crunching.

One or two sachets of the Fermentis yeast into the brew has made no appreaciable difference to my lagers.  With just one sachet, I have had a slightly fruitier brew but this conditions out in the bottle.   I ferment at 12°C and the fermentation takes three weeks regardless of whether I have pitched one or two sachets of yeast.  The only time I managed to reduce the fermentation time was when I pitched 30 gr of dried Brewferm lager yeast but part of that could be due to the yeast strain.  I have also used fresh yeast slurry and still found that my brews required three weeks to ferment out.  None of this is scientific of course.

Conclusion => interesting reading but mostly inapplicable to my rudimentary brewing system.


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Pesho77

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 Im still happy to ferment at 20c and call it a lager.

 Pesh
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Clibit

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Reply with quote  #11 
Quote:
Originally Posted by Pesho77

 Im still happy to ferment at 20c and call it a lager.

 Pesh


With a true lager yeast?


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Womble

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Reply with quote  #12 
I did a false lager with US05 once ... fermented the brew at 15°C and it came out okay. 



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Pesho77

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Reply with quote  #13 
Quote:
Originally Posted by Clibit


With a true lager yeast?




 Yes but only because I have some in my freezer.

 Pesh
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Clibit

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Reply with quote  #14 
Quote:
Originally Posted by Pesho77


 Yes but only because I have some in my freezer.

 Pesh


Why do you choose to ferment at 20C if you can do it cooler? Fridge space?
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Pesho77

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Reply with quote  #15 

 Its quicker for the same result

 Pesh
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