Purpose of lagering?

brewmonger · 03-06-2009, 04:52 PM

Besides storage, what is the purpose of lagering beer?

**culaslucas** · 03-06-2009, 05:39 PM

I suppose I'm confused by the question. A lager is produced by different yeast strains than ales. These yeasts prefer cooler temperatures to do their dirty work, are 'bottom fermenting' & take 2-3 times longer to ferment than an ale. These differences produce distinct characteristics typical of a lager. Those being, crisp, less fruity/spicy than an ale.

The purpose? hell if I know, I'm an ale guy!

menschmaschine · 03-06-2009, 05:52 PM

This is from Brewing, Science and Practice that sums up what is happening during beer maturation (particularly lagering):

Quote:

Several important groups of compounds have been identified as changing during the
maturation of beer with consequent positive effect on beer flavour. The most important
are: diketones (especially diacetyl), sulphur compounds, aldehydes, and volatile fatty
acids.

Essentially, these flavor-active compounds are reduced, resulting in a cleaner beer (essential in lager beer). Additionally, the dissolved CO2 (higher at low temps) helps to condition the beer and reduce the effects of oxidation. Lager yeast can also "gnaw" at a few extra sugars during lagering, but the effect is usually no more than 1 or 2 points of gravity reduction.

There are probably a few other mechanisms going on, but without Noonan's book in front of me, I can't recall exactly. Perhaps someone else can chime in.

**Mutilated1** · 03-06-2009, 06:00 PM

I was wondering the same thing.

And why do you have to lager big beers for a longer time, where you can lager an American lager for 2-3 weeks and thats plenty ?

And also why does it have to be so cold for lagering, other than the obvious fact that it causes more of the yeast to fall out ?

menschmaschine · 03-06-2009, 06:12 PM

Quote:

Originally Posted by Mutilated1

And why do you have to lager big beers for a longer time, where you can lager an American lager for 2-3 weeks and thats plenty ?

I believe the more sugars that have been fermented (higher gravity), the more of the compounds I mentioned above (plus more potential for higher alcohols, which get reduced to other compounds during lagering), hence the need for longer lagering. There may be more to it than that though.

Quote:

Originally Posted by Mutilated1

And also why does it have to be so cold for lagering, other than the obvious fact that it causes more of the yeast to fall out ?

Perhaps this has something to do with it: colloidal stabilization. (Lower temperatures promote colloidal stabilization.)

Kaiser · 03-06-2009, 09:46 PM

There are 3 phases to a lager fermentation: primary fermentation, maturation and cold stabilization. Depending on the fermentation schedule these might be distinct from each other or flow into each other. The classic German fermentation schedule is a nice example for these phases flowing into each other.

If we talk only about the cold storage aspect of lagering it is mainly for precipitating haze and clearing the beer (the colloidal stabilization that Mensch mentioned). Some modern breweries shorten this process by filtering the beer after it has been sitting cold for only a few days. But I prefer to let the haze settle for a 4-8 weeks. After that I don't have to filter, which is always a pain and I don't see it justified anymore.

I noticed that the development of flavor (as you know it from Dunkels, Bocks and Doppelbocks) goes faster at cellar temps and that's why I only lager these beers for up to 2 months now and then rack them off the sediment and age them for another few months.

If you actually count on significant fermentation activity during the lagering phase you may have to keep the beer at these temps for more than 2 months.

And I also think that you can make a lager w/o lagering it. It won't be as good as it could be, but still pretty good.

Kai

flyangler18 · 03-06-2009, 10:05 PM

A related question (and I really should create a new thread on this) is the importance/relevance of a graduated decrease in temperature for lagering. Kai, I seem to recall you saying you go straight to lagering temps after primary fermentation has concluded rather than stepping down incrementally over a period of time before reaching lagering temperatures. Can you shed some light on this?

Jason

**david_42** · 03-06-2009, 10:12 PM

Lagers take longer because they are conditioned near freezing and that slows the process down.

Kaiser · 03-06-2009, 10:53 PM

Quote:

Originally Posted by flyangler18

Can you shed some light on this?

If your fermentation is not complete, i.e. diacetyl not sufficienctly reduced or the amount of residual fermentable sugars is still to high for the style, when you lower the temp to lagering you'll have to lower the temp gradually in order to keep the yeast as active as possible. But if this is not the case, which is generally the case with the extended primary fermentation or the warm diacetyl rest, then there is no need for that. This is one of the aspects that is incorrectly explained in Parmer's and Noonan's books.

Kai

flyangler18 · 03-06-2009, 11:04 PM

Quote:

Originally Posted by Kaiser

If your fermentation is not complete, i.e. diacetyl not sufficienctly reduced or the amount of residual fermentable sugars is still to high for the style, when you lower the temp to lagering you'll have to lower the temp gradually in order to keep the yeast as active as possible. But if this is not the case, which is generally the case with the extended primary fermentation or the warm diacetyl rest, then there is no need for that. This is one of the aspects that is incorrectly explained in Parmer's and Noonan's books.

Thanks Kai! I've not yet read Noonan, though I know that the rate of temperature decrease is a point of contention among some of my HBT fellows.