Filtering/Lagering

[ajdelange]

When I cool my lagers at the "completion" of fermentation and hold at 33 °F:
1. Gas continues to be evolved (not much mind you, but enough to maintain pressure is a slightly leaky fermentor for quite a while)
2. VDK's get absorbed
3. Gravity continues to drop (again, not spectacularly sometimes only 0.1 °P, sometimes as much as 0.5°P)

all of which I attribute to continue activity of the yeast.

Other things happen too and these, the melding of flavors, the passage of volatiles, formation of protein/phenol complexes..., may not be yeast mediated but those three items I listed I believe to be.

This is not the way a modern brewery makes lager. They use diacetyl rests to speed the process. It makes good beer. Almost as good as the traditional way. That last crack was a bit tongue in cheek. I doubt I could tell the difference in a blind tasting. If you include a proper diacetyl rest as part of a "good fermentation" then I think you are probably right but that is a replacement for the traditional lagering. If you read up on this you will frequently find references to lagering with the keg on the side. This is to give the yeast a larger area to spread out over so that contact with the lagering beer is maximized. If the yeast weren't doing anything that wouldn't be necessary.

[Buttwidget]

Very interesting stuff, thanks for spending the time to explain... A couple of questions:

1. I'm not seeing any pressure being built up in my fermentor, I've checked for a good seal and am wondering when this yeast is going to get hopping (if it will). Seriously, over a week and no movement whatsoever. At what temp does yeast stop working? I know freezing yeast will kill it, so 33 degrees (F) means 99% death?

2. What are VDK's?

3. I don't check gravity unless I am racking between vessels... I guess I need to come up with a sanitary process to pull a sample to check gravity during lagering. Although, wouldn't one observe a drop in gravity at that level/rate just due to the precipitation of the solids/proteins from the beer? The drop isn't necessarily explained by yeast activity, is it?

Even with a diacetyl rest, I think lagering is important to helping the flavor profile of the beer. I'm not sure about the effect of yeast, yet. I guess that's what I'm trying to learn.

Again, thanks for your time and patience in helping me to understand.

Buttwidget

[animaldoc]

1. No real input so I'll move on to

2. VDKs - vicinal diketones. Acetaldeyhyde, diacetyl. Metabolic intermediates that the yeast can leave behind or clean up given the proper conditions.

3. Suspended particles don't affect SG (I believe) it's only *dissolved* solids. My guess is the amount of protein that contributes to haze is so small it won't affect your measurement of the gravity

[ajdelange]

Very interesting stuff, thanks for spending the time to explain... A couple of questions:

1. I'm not seeing any pressure being built up in my fermentor, I've checked for a good seal and am wondering when this yeast is going to get hopping (if it will). Seriously, over a week and no movement whatsoever.

That's not so encouraging. You hope to see a pH drop within a couple of hours, scintillation at the surface within another few hours, foam islands within another couple of hours after that and then gas evolution. Certainly there should be gas evolution within 48 hrs of pitching. You might try gentle agitation to see if the beer is fizzy.

At what temp does yeast stop working? I know freezing yeast will kill it, so 33 degrees (F) means 99% death?

I don'tg think there is a fixed number. Cetainly metabolism will be slow at and below freezing but they should stay alive until frozen and even past that point if protected with glycerine.

2. What are VDK's?

Vicinal (means next to each other) diketones i.e.. diacetyl (CH3COCOCH3) and 2,3, pentane dione (CH3COCOCH2CH3). The CO's being next to each other is responsible for the "vicinal". Acetaldehyde is not a VDK but does get cleaned up during lagering as well.

Although, wouldn't one observe a drop in gravity at that level/rate just due to the precipitation of the solids/proteins from the beer? The drop isn't necessarily explained by yeast activity, is it?

If dissolved protein complexes with a dissolved phenolic and they come out of solution, then yes. Both are part of "extract" and, as such, extract, and hence SG, decline. But there is residual fermentable sugar at this point as well. When the yeast consume it the extract is also diminished and hence this is another mechanism by which SG is reduced. Undissolved particles do not effect SG. They either float, sink or are of the same density as the solution. Only in the last case would they be captured in an SG measurement but as they are of the same density as the solution they don't effect SG. This may seem silly but if you float a hydrometer in a swimming pool and then toss in bowling balls and chunks of balsa wood the hydrometer reading isn't changed.

Even with a diacetyl rest, I think lagering is important to helping the flavor profile of the beer. I'm not sure about the effect of yeast, yet. I guess that's what I'm trying to learn.

Yes, it is. Breweries that do diacetyl rests still lager if only for a week or so.

[animaldoc]

2. What are VDK's?

Vicinal (means next to each other) diketones i.e.. diacetyl (CH3COCOCH3) and 2,3, pentane dione (CH3COCOCH2CH3). The CO's being next to each other is responsible for the "vicinal". Acetaldehyde is not a VDK but does get cleaned up during lagering as well.

Thanks for the correction AJ .... it was late, I was enjoying a libation, and I haven't balanced a chemical equation in 15 years

[dirtyal]

I´ve been using gelatin since 2009, I think, for the homebrewer, is a better why to clarify the beer than filtering.