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I've just made my first lager, it is currently lagering at 1 C. What is happening to my beer at this temperature? Is the yeast still active? And most importantly: What is happening at this temperature that would not at higher temperatures?

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Lagering temp adjustments are done gradually not like a cold crash.

Lager yeast strains are very much alive and active during lagering. The colder temps slow the yeast metabolism, they are struggling to survive, the byproduct is they consume phenols and other things they made or ignored during primary.

Story Time - here's a little illustration, you're in the snow near freezing starving and have no energy and are near death the only thing available to eat is the grease soaked paper wrapper from the burger you had 2 weeks ago in your pocket, you bet you eat it. But If you have the energy to prepare or search for easier food you won't. This is basically the situation lagering puts yeast in.

1°C - The lower the temp, the slower the yeast are to clean up. 1°C is the usually a temperature for a several month lagering. Raise temp to reduce lagering time at the trade off of quality. Low and slow is the way for quality.

  • So if I tried "lagering" at a higher temperature, lets say 10 C, the yeast would not consume these fermentation byproducts? In the context of your story, I would eat that grease soaked wrapping paper when I got hungry enough, regardless of temperature. – arnefm Jan 11 '16 at 16:33
  • @arnefm exaclty, but since lager yeasts differ you don't want them to be to warm and active or they can find it easier to eat the dead yeast. Follow the recommended temperatures for your specific strain. – Evil Zymurgist Jan 11 '16 at 16:36
  • I'm using White Labs WLP833 German Bock Lager Yeast. I've kept the temperature in the recommended range. Fermented at 10 C, diacetyl rest at 16 C and lagering at 1 C. I have plenty of time and I want this bock to be perfect, so I'm willing to lager it for as long as 6 months if necessary. – arnefm Jan 11 '16 at 16:43
  • @arnefm I to will be doing a dopplebock next week, growing 1,200+b cells for a the pitch. It will lager for about 6weeks. If we had more time it would be better, but we hope the large pitch will produce less phenols for lagering to clean up. Bottomline is taste it, if you would drink it as it is a short lager time is all you need. If it's hot or got phenols let it ride, if you have 6months let it chill for it. – Evil Zymurgist Jan 11 '16 at 16:53
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The primary thing that is happening is that stuff is dropping clear. The cold temp in combination with sitting still for extended time allows even the smallest of insoluble particles settle out of the beer.

Secondary may be some yeast activity, but its very slow. I have made plenty of lagers and much of the yeast work is done before you do the lager phase. When fermented right many lagers taste great even without the lager phase. I have often gone right to serving a lager just 6 weeks into the process and those beers went into the lager phase. That's not to say the beers would be even better with an extended lager phase.

In theory a good lager ferment doesn't leave much 'clean up' for the yeast to do. If a diacetyl rest was performed then the higher temp encouraged the yeast clean up thing to happen then, before lager phase.

So ultimately at 1C for a month its all my first point, clarity. Keep in mind that with clarity the dropping yeast pull with it certain flavor compounds.

  • So it's the same as cold-crashing ales? I've fermented my doppelbock (OG 1.081) at 10 C for 24 days, then raised the temperature to 16 C for 2 days (diacetyl rest). After that I transferred to secondary (FG 1.014 (!)) and lowered the temperature to 1 C. I'm planning on leaving it at this temperatere for 10-12 weeks. – arnefm Jan 11 '16 at 13:45
  • Basically yes, IMO and experience. There's nothing magical about the lager phase to making lagers. Its the cooler fermentation tolerance of the lager yeast, that makes for clean fermentation profiles during fermentation. The rest of it is just cold storage. Those cooler tolerant yeasts might have more activity than an Ale yeast at lager temps, but in the grand scheme of total activity there really is very little yeast activity once you go to lager temps in ale yeast and lager yeast. – brewchez Jan 11 '16 at 20:08
  • regarding your dopplebock as yourself this question: "How does it taste now?" You might want to package some and start drinking it. Lager the rest and then see if it matters. – brewchez Jan 11 '16 at 20:10
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Your beer is developing the clean crisp flavour profile associated with lagers.

The yeast is still active, this is one of the main distingushing factors of a lager yeast is it doesn't beome dormat at low temps but continues to ferment, even if slowly. Still any sudden drops will cause dormancy.

The main thing happening to your beer is the break down of sulphur compunds(H2S), lager yeast tends to produce more sulphur off flavours than other yeasts, but during lagering cleans these up. Some other off flavours are also broken down.

Also as already mentioned it allows the beer to drop clear.

Regarding time to lager 3-4 weeks at 3C should provide time for the clean up to occur once primary fermentation has reached 1-2 points off final gravity and you have done your diacetyl rest.

You don't have to leave it for months, but this can depend on the strain of yeast used and the higher the OG the longer the lager, so with a 1065 OG you may leave it 3 months, and some yeasts produce far more sulphur compounds than others and require longer to remove them from the beer.

  • I might have messed up then, I lowered the temperature to 1 C immediately after the diacetyl rest. Is there a way to salvage this, perhaps by slighly raising the temperature again? – arnefm Jan 11 '16 at 16:35
  • so long as you lowered it slowly to 1C you should be fine, if you did this over a day or so it should be alright. if you crashed it down in 4 hours your yeast will likely have dropped into a dormant state. Allow to warm back up to fermentation temp, leave for 12 hours then slowly bring down to your desired/specified lagering temp. – Mr_road Jan 11 '16 at 17:03

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