Adding finings to finished beer in pressurized corny

[HighCountry]

I'm mostly wary of letting off CO2 and thus denaturing the proteins that provide head retention/mouthfeel.

I'm not a biochemist so can you explain in layman's terms how degassing will denature protein? Thanks

I'm certainly not a biochemist, either, but I'll do my best to explain my thinking. JZ and Palmer did a great job covering this concern in the podcast on head retention. Therein they point out that the proteins that form and retain head are formed only once. This happens when the CO2 comes out of solution and builds the foam that we know as head. But since these proteins form only once and then drop out, certain practices stand the chance of causing gas to come out of solution, forming foam and reducing head formation and retention in future beers poured from that batch. Agitating the beer during transfers, allowing too much beer to blow off during fermentation or allowing the beer to degass and form head are all methods of potentially causing the loss of head formation and stability.

My concern (and I think I was quite wrong) was that by unlidding the corny I would allow the release of CO2 from the beer and cause the loss of some head retention. I think jwatkins is right when he says that you'd have to actually agitate the beer when adding the gelatin mixture to cause gas to come out of solution, build head and lose the proteins. The formation of head is not necessarily a chemical reaction (yet it is), but the result of the mechanical disturbance of beer causing the CO2 coming out of solution and build head.

So I added the gelatin directly to the finished beer. There was a little foaming (AJ pointed out that certain finings act as nucleation sites and cause foaming in finished beer) and a nice blanket of CO2 hanging over the beer. I'm sure it will be fine.

[Sent From My iPhone]

Yeah, I remember the episode and just went back to relisten. I was just curious how degassing would actual denature the protein. He did say the proteins are formed and used only once, but nothing about the proteins being denatured.

However, I believe you can degas a keg without forming a lot of foam and therefore not effect foam formation and head retention. I've done it by slowly degassing a keg over the course of a week or so to filter (most recently a Kolsch) and then recarbing. Didn't seem to effect the head. Many times I've unhooked a carbonated keg from the CO2, only to comeback to a it a few weeks later to find I had a gas leak and the beer was flat. Recarbonated it fine.

[Thirsty Boy]

a) Depressurizing your keg wont hurt the head. I am skeptical of the JZ/JP assertion that head forming protiens happen only once. I shake the crap out of my kegs to carbonate them, also when using a carbonation cap to gas up individual PET bottles - lots and lots of foam happens. But I have never ever had a head retention issue. The tiny tiny amount of fob you might get from gassing off you keg - is going to do absolutely nothing at all.

b) Unfortunately gelatin is not really going to help your chill haze much. Perhaps a little but that's it. Gelatin mainly works on yeast by causing them to clump together.

Different finings for different things:

Gelatin - mostly yeast haze, little effect on chill haze.
PVPP - chill haze and nothing else, basically no effect on yeast.
Silica Gel - as for PVPP
Isinglass - Mostly works on yeast but does reduce chill haze if it added to cold beer where the chill haze has already formed.

Really PVPP and Silica gel aren't even fining agents. They are process aids and don't act on actual haze causing particles, they remove the chemical components that combine to form haze in the first place.

If I have to add finings ot a carbonated keg, I do so by depressurizing and injecting it through the gas in post. Just a 20ml syringe and a couple of goes does the trick.

Hopefully the gelatin does the trick for you in spite of what I just said.

TB

[HighCountry]

Yeah, I remember the episode and just went back to relisten. I was just curious how degassing would actual denature the protein. He did say the proteins are formed and used only once, but nothing about the proteins being denatured.

However, I believe you can degas a keg without forming a lot of foam and therefore not effect foam formation and head retention. I've done it by slowly degassing a keg over the course of a week or so to filter (most recently a Kolsch) and then recarbing. Didn't seem to effect the head. Many times I've unhooked a carbonated keg from the CO2, only to comeback to a it a few weeks later to find I had a gas leak and the beer was flat. Recarbonated it fine.

You're right on a couple of levels. 'Denature' was probably not the correct word. It's not like the proteins are broken down into amino acids because of the mechanical release of gas. I apologize for (drunkenly, probably) typing the wrong word.

Also - I've successfully degassed kegs the same way you've described, as well. You're absolutely right that it doesn't seem to affect the head formation/retention. But slowly and carefully letting the gas come out of solution is different, I think, than suddenly, mechanically releasing the gas and causing head to form. There, I think, is the point that JZ/JP were trying to make in the podcast. But I could be wrong. I'm sort of drunk right now. Market research night!

[HighCountry]

a) Depressurizing your keg wont hurt the head. I am skeptical of the JZ/JP assertion that head forming protiens happen only once. I shake the crap out of my kegs to carbonate them, also when using a carbonation cap to gas up individual PET bottles - lots and lots of foam happens. But I have never ever had a head retention issue. The tiny tiny amount of fob you might get from gassing off you keg - is going to do absolutely nothing at all.

I suspect you may be right. I've experienced the same thing when filling party pigs with finished beer. Depending on how careful I am that can cause a significant amount of foaming inside the pig. Still, after the O2 has been purged and the beer poured from the pig you have to use steel wool to get the lacing off the glass.

Also, Thirsty Boy, thanks for the clarification on the utilization of finings. I haven't used any for a while, and you're right. I may have picked the wrong fining to address my chill haze. I'll report back here to let you know what happens.

All this for a beer audition. And I've forgotten to mention that the hazed beer that this forum is addressing has been otherwise a really successful batch. It tastes great, but those haze problems really complicate things. As my wife, the chef, says, first you have to feed the eyes. The psychological perception of quality is important. Malcolm Gladwell covered the issue well in "Blink". Not extraordinarily important to this forum, but interesting in terms of the background for my concern about the chill haze.