Lager fermentation

[BrianL]

I'm reading Noonan's book on Lager brewing (really good book) and he says to start turning down the temperature from 50 down to lagering temps (40 or so) towards the end of the primary fermentation phase. I'm doing my first lager now. Pitched at 44, raised to 50 over 2 days, been holding it steady there and the krausen is just starting to come down after a week.

I'm debating:

1. Leaving it at 50 until everthing appears to be done and then slowly cooling it to 40 before racking into a keg for lagering.

or

2. Start running the temp down slowly over the next couple weeks as Noonan suggested.

Seems like leaving it warm a little longer would help the yeast clean up. I don't plan on a diacetyl rest since I pitched cold.

Any thoughts?

[BrianL]

Great info here http://www.braukaiser.com/wiki/index.php?title=Fermenting_Lagers#When_to_rack_the_beer

Still debating which route to go

[ajdelange]

I let it ferment at 47-48 °F until gas evolution slows, spund at that point and then watch the pressure. When it stabilizes (a couple of days later) I take it down a couple of degrees per day to get it as close to freezing as I can and hold it at 33-34 °F until I'm ready to keg so it's usually lagered perhaps 3 weeks in the fermenter (in addition to the primary period of about 10 days) before going into kegs. The good news here is that it only takes a couple more weeks lagering before it is drinkable (if not great).

[Bruck]

I would suggest a diacytal rest first.

[Kbar]

I would suggest a diacytal rest first.

+1

[Stinkfist]

I would suggest a diacytal rest first.

+1

+2 not only does it reduce diacytal but it will also make sure fermentation has really completed before you drop the temp too cold

[ajdelange]

I would suggest a diacytal rest first.

A "diacetyl" rest is not necessary (or really beneficial) if you intend to carry out traditional lagering. In this case the wort would be transferred when fermentation is nearly complete making sure that quite a bit of yeast gets carried over to the lagering vessel. Having the yeast is very important as it is they that will consume the diacetyl as it is formed. No yeast, the diacetyl stays in the beer.

If you are looking for faster lagering and/or transfer clear beer to the lagering tank then elevated temperature will speed the degradation of acetolactate but then yeast need to be added back in to clean up the diacetyl formed in this process. The usual compromise is to raise the temperature while the yeast are still in suspension but not to raise it to the point where the yeast are damaged so that they can clean up the diacetyl at the end of the rest.

The diacetyl rest (which is really an alpha acetolactate rest) is the child of modern commercial brewing practice in which 3 months (the traditional time period) lagering periods are not economically feasible. Of course the homebrewer can do it any way he wants: tradional, quick or something in between.

My lagers, when I used to check it, generally showed diacetyl concentrations around 0.1 mg/L which is right at the threshold and just where it ought to be (IMO) in most lagers but especially in Bohemian Pils where it is an important part of the style. I have never used diacetyl rests. I was, several years ago, talking to a professional brewer who opined "There is no place for diacetyl in lager beer." I asked him if they knew that in Pilsen (0.2 mg/L diacetyl).

Note WRT the diacetyl levels mentioned: the reported value for diacetyl given by the ASBC methods (except chromatography) include 2,3 butane dione and acetolactate and so are really measures of "diacetyl potential".

[Thirsty Boy]

+1 to AJ

If you are going to go with a raised temperature D rest, then you can skip the majority (if not all) of the slow cooling down period. You will most likely hit acceptable D levels a couple of days after you hit terminal gravity.

No raised temp and a cool down to near freezing over a few weeks... then its going to take closer to 21days to hit acceptable D levels.

Doing both is a mish mash of two methods that are incompatible - it wont hurt, but its a waste of your time and effort.

Me - I spurn tradition at every point where I am not convinced it adds value - so I raise ferm temps after 2/3rds attenuation - finish out the beer to a full stop at the higher temp, crash, fine (gelatine and PVPP) filter, carb, drink. Maximum time from brewing to drinking about 6 weeks and I don't believe my quality suffers one iota as compared to those times when I have gone through the months of PITA involved in brewing a lager traditionally.