Lost Foam?

[menschmaschine]

We've talked before on here about foam produced during brewing and/or fermenting being "used up"... i.e., if you create foam by shaking, etc., it would be lost. I've been fairly skeptical of this notion because I figure, in order for the foam to be "lost", the responsible proteins would have to come out of solution and stay out of solution. So, wouldn't it form a haze or sediment?

Anyway, I wouldn't be surprised if there is some merit to the notion of losing foam permanently, since I've heard it from several sources. But I've never heard it explained, only stated.

Of course there is the article by Chris Colby for BYO (Dec. 2005) that states:

...homebrewers who keg their beer should be aware that foam positive molecules can get “used up” when foam is created. Thus, if you shake your keg to carbonate it, you may be dipping into your pool of foam makers for your beer.

But this still doesn't explain where these "foam positive molecules" go. So, if someone knows something I don't regarding this, please let me know. I did, however, stumble across this statement while re-reading Noonan's New Brewing Lager Beer:

The increase in the alcohol content of the beer induces the reabsorption of the albuminous matter into solution.

The context for that quote is krausen falling back into the beer at the end of fermentation. But since major foam constituents are albumins, wouldn't the same principal apply for foam at any post-fermentation stage?

 

[SpanishCastleAle]

It's those damn foam trolls.

After our previous discussion on this I did a very scientific experiment of filling two identical 0.5L growlers but I left quite a bit of headspace in each one (headspace was virtually identical for each). Then I put them in the fridge and over the course of the next month or so I shook up one of those growlers everytime I opened the fridge...the 'control' bottle just sat on the same shelf behind the 'shake' bottle.

Then I compared them about a week ago or so. Zero difference...both had great head.


But let me throw this out there: At my job we have a closed-system/tank with a surfactant solution in it...it's nothing but DM water and 25ppm of a surfactant called 'Zonyl' (lowers the surface tension). We have a pump connected to the tank, a back-pressure regulator at the pump outlet (with requisite 'bypass' line back to the tank), as well as a 'return' line back to the tank (sink drains go to pumps that pump it back). When we first set this closed-system up; the measured surface tension of the solution would be fine but then would quickly increase to above spec. Why? Because the bypass line from the BP reg back to the tank flows a LOT and causes foaming in the tank...all the surfactant was 'in the foam' and no longer in the water. We had to set-up an upside-down lawn sprinkler inside the tank (tee'd into the bypass line) to knock the foam down and the problem totally went away. So in our case, it appears the foam-positive compound(s) were 'used up' only when they were still 'in use'...as soon as the foam went down those foam-positive compound(s) went right back into solution.

Maybe they're saying that if there is a bunch of foam inside the keg that those foam-positive compounds are unavailable to be dispensed?

 

[menschmaschine]

Maybe they're saying that if there is a bunch of foam inside the keg that those foam-positive compounds are unavailable to be dispensed?

I like your experiment... simple and effective. I would think foam from shaking a keg would dissipate pretty quickly. So, yeah, if you're dispensing beer immediately after shake-carbing, I could see the foam being reduced, but letting it sit for a few hours would dissipate that foam, so if it was "lost" it would either create a hazy beer with little head or settle to the bottom and come out of the keg upon first tapping. If it's not "lost", it would be reabsorbed into solution.

Then of course there's this quote from Cargill Malt on Probrewer:

And finally, a word on the head retention issue. One very important thing to remember is that the wort entering fermentation has a set concentration of hydrophobic head forming proteins in solution. Said proteins give you the head and lacing you are looking for. Since these proteins are hydrophobic (water hating) once the come out of solution they stay out of solution. Take home message is that every time you make foam in the brewing process that foam is foam that will never make it to the customers glass. All malt wort has plenty of foaming potential without help from foaming aids etc. But if this potential is squandered through rough transfers, transferring into tanks without top pressure, or excessive in-tank carbonation or oxygen scrubbing with CO2, you will wind up with a less than stellar presentation in the glass. So keep those proteins in the beer where they belong.

I shake the crap out of my fermenters for aeration and I have good foam and foam stability on all my beers (now... I didn't always due to improper protein rest temps and other mistakes).

So, I just haven't seen anything to convince me this whole "lost foam" idea is true.

 

[SpanishCastleAle]

I agree with you.

I'm not familiar with the process but what about those inline carbonation 'stones' that many brewpubs use? When they transfer the beer the inline stone carbs the beer...does it make a bunch of foam?

TBH, I haven't even noticed a correlation between blow-offs and head retention. With a blow off you're supposedly losing a bunch of head positive compounds forever...but my blowoff beers have big, moussy heads just like the non-blow-off beers do. I see no difference but I haven't put it to a test.

 

[fratermus]

I've been fairly skeptical of this notion because I figure, in order for the foam to be "lost", the responsible proteins would have to come out of solution and stay out of solution. So, wouldn't it form a haze or sediment?

I, too, am agnostic about foam consumption, but I could imagine a third possibility the proteins stay in solution but lose their foam-positive properties.

I am a fan of blowoff (including the use of 5gal carboys for 5gal batches) and have also seen no correlation between agitation or blowoff and head formation/retention. I think the biggest difference for me is serving temp and the "beer clean" status of the glass.

I like the growler experiment!

 

[menschmaschine]

I'll have to recheck Noonan later tonight, but I recall reading an irony in all of this that skimming off krausen (or blow-off loss) is good for the beer in regards to foam/stability. I'll check later and post back.

 

[menschmaschine]

I'll have to recheck Noonan later tonight, but I recall reading an irony in all of this that skimming off krausen (or blow-off loss) is good for the beer in regards to foam/stability. I'll check later and post back.

I'll have to rescind that statement. I can't seem to find it. I may have been thinking of overall beer stability being better when the krausen is skimmed off. He does say that (skimming the krausen or removing the beer from the trub immediately after primary fermentation).

 

[pjj2ba]

Ok, I'm set up to test another variant on this. I've got a flask of freshly autoclaved "media" (leftover wort) on the bench in lab. Actually it's two, but since I only need one right now, the other one is now an experiment. I'm assuming Spanish Castle, that your experiment was with beer, not wort. Your experiments would indicate that in beer, the foam is not lost. The other question then is, what about the stages before it is beer? So it looks like once it is fermented, the foam potential is locked in. However, steps we take in the preparation of our worts clearly affects head. Does this also include excessive foaming prior to fermentation? I'll just keep periodically shaking the flask and we'll see what happens.

 

[menschmaschine]

Does this also include excessive foaming prior to fermentation? I'll just keep periodically shaking the flask and we'll see what happens.

Sounds good. But if foam can be "lost" in wort, wouldn't everyone who shake-aerates have poor foam/stability? I shake-aerate and I've not noticed poor foam/stability.

 

[SpanishCastleAle]

Yes pjj2ba, it was beer from a keg.

If it is true in wort then at what point would it get 'locked in'? I ask because the fermentation process itself makes a ton of foam...which is sometimes blown-off or skimmed.

 

[pjj2ba]

I'm thinking the yeast may be modifiying the foam positive proteins. Actually, I do know they do this. I suspect the foam might be locked in once the bulk of fermentation has stopped.

It's only one day into my test, so this is a VERY preliminary result. This starter is from a leftover wheat beer (50:40:10 wheat, Pils, Munich) and is going to have some rocking head :rockin:. It still had a little foam after shaking 24 hrs prior (the other flask). It looks like the same as SpanishCastle found that the foam positive proteins might be temporarily used up. The first good shake made about 2" of foam. If I shake it within an hour (still some foam left before shaking). It doesn't foam up as much. Same thing this morning. Huge head on the first shake, much less on subsequent shakes.

 

[pjj2ba]

Update time. We'll in unfermentened wort, it appears as though shaking results in no loss of foaming in the long term. My flask got shook every work day for nearly a month. It foamed up great every time. Any oxidation over that period didn't seem to be a problem. The flask was just covered with foil, not sealed.

So, as long as the foam is allowed to settle back in it looks like foam proteins don't get used up.


At least in a really foamy wheat beer wort

 

[menschmaschine]

Thanks pjj2ba for the follow-up. You've affirmed my suspicions.

 

[kanzimonson]

Foam gnomes

Phase 1 - collect foam

Phase 3 - profit

 

[lamarguy]

Sorry to resume an old thread from the graveyard, but it was linked as a supporting post.

Polypeptides, proteins, and iso-alpha-acids all combine to form a good beer head. This should help explain the importance of protein in beer foam. From Beer: quality, safety and nutritional aspects By E. Denise Baxter, Paul S. Hughes:

Foaming during beer production can lead to the irreversible loss of foam-active species. Irreversible denaturation of proteins, a process perhaps essential to the formation of beer foam, generally reduces protein solubility. Thus foaming will result in a loss of a proportion of foam-active proteins from the bulk beer. Paradoxically, the use of silicone antifoam agents during fermentation is beneficial to final beer foam stability....This is on account of the suppression of foam head during fermentation, with attendant reduced losses of protein.

Some of the essential foam forming agents (e.g., polypeptides and iso-alpha-acids) are reabsorbed post-fermentation (i.e., not lost to krausen deposits) but the foam positive proteins do NOT get reabsorbed since they are, well, denatured. A subtle yet important distinction.

So...Yes, it is correct to say that an essential foam positive agent (protein) is inherently destroyed upon foam creation.

 

[menschmaschine]

I would like to see this explained scientifically. It gets stated, but never explained... i.e. they are destroyed or denatured. How? What is the catalyst? Is it oxidation? What happens to these proteins? How does this relate to Noonan stating that albuminous matter is reabsorbed into solution as facilitated by the alcohol content?

The only potentially plausible reasoning I can think of would be if they are denatured somehow (e.g., oxygen), reduced to smaller molecular weight proteins which are not "foam positive", and reabsorbed into solution never to come out again as foam. Still, this would go against the results of pjj2ba's experiment in this thread.

 

[lamarguy]

I would like to see this explained scientifically. It gets stated, but never explained... i.e. they are destroyed or denatured.

FWIW, I attempted to help explain the protein denaturation process in this thread.