Nitrogen Fairy Tales

[mr.jay]

I'm hearing many different versions of a story that should have just one. When I ask people (rather brainy people, mind you) they tell me their version as if it's fact, and that, "everyone ought to know this because..." Here it goes. Some are saying that nitrogen does not get dissolved into beer. It simply cannot. It is merely an inert gas that pushes a small amount of CO2 through some plates that essentially "whip up" the head, and create a creamier beer as the result. They say any inert gas, even argon would work. That no nitrogen is present in the beer. That it is simply a myth to believe that those tiny bubbles in our stouts are the result of nitrogen I've heard that nitrogen can't be absorbed below 35 psi. I've heard others say it can. Others say, that gas IS nitrogen in the beer, and the reason it cascades is because there is Nitrogen in the atmosphere, and remains in equilibrium, so it never releases itself from the solution. I could go on with other convincing stories, but I would rather hear the truth from somebody who REALLY KNOWS, and doesn't begin with, "well I heard it's because..." As brewers, we need to be informed, and there is nothing worse then passing on wrong information because it sounds possible in theory. With this whole Nitrogen thing, all of these versions can't be true, and I have heard many. Can we have the real story from somebody who knows for sure. Many of us are yearning to know. From the carbonation process to the pour, how does it all work!
Signed,
Frustrated!

[jhuck]

I think the confusion is between "dissolution" and "reaction". Nitrogen, an inert gas, does not "react" with most other elements or compounds (including the chemicals in beer). CO2, though not a noble gas, is stable enough that it doesn't react with the other chemicals in beer as well. That is a good thing; if they reacted they would change the entire chemical makeup of beer, probably making it undrinkable.

Dissolution of a gas is an entirely separate concept, governed by the Ideal Gas Law, PV=nRT.

In a sense those "brany people" are correct. There is no nitrogen, or CO2 in beer... Those elements and compounds have not joined with any of the other chemicals in the beer, and they can be removed simply by reversing the dissolution process.

If they are suggesting that there can not be dissolved gasses within a liquid, however, they are simply incorrect. (Fish would not be able to live if there were not O2 dissolved in H2O.)

Hope that helps...

JH

[Eleusis]

The tiny bubbles that make the creamy head are definitely nitrogen. How much gets dissolved, if any, I couldn't say.

Here's an article, though it's more geared toward Guinness cans.

[RobZamites]

Yeah, well, I'm perplexed too. There was a previous thread discussing "nitrogenation" of stouts, etc. and basically what I gleaned is that the only way to truly do that was to have your beer: a) very cold and b) apply pure nitrogen to it at over 35 PSI.
Now, I don't have the means to purchase a serving tank rated for such pressures, and the idea of wrangling/cleaning kegs for the sake of "nitro" stout doesn't exactly appeal to me, either.
What I want to know, is if *anyone* on these forums uses/has used/has opinions on the "Cellarmaster" -- because if it performs as advertised, I think I could be convinced to spend the $1000 or so for that in lieu keg-wrestling. Of course, I just might give up the whole idea of a "nitro" stout and pour regular stout from a standard tap. *shrug*

[VTBrewer]

I have found that in my brewery simply "nitroing" a beer is simple. Airstone, 26 psi, and temp at 38 degees, slowly "nitogenate" for six - seven hours and you have that wonderful creamy stout.

[crassbrauer]

Law of Partial Pressures

What you guys were referring to above is the Law of Partial Pressures (or Dalton's Law). To get a clearer picture of what's going on it might be good to have a look at it, along with PV=nRT. It's in any physics book and can also be found at this link:

http://en.wikipedia.org/wiki/Partial_pressure

It explains the behavior of N2, O2, CO2 in beer and what happens when mixed gas is used. All of these gases physically dissolve in the liquid, i.e. without breaking apart into their component atoms - there's no chemical reaction. (Only a tiny part of the CO2 in beer forms carbonic acid; mostly it's inert, i.e. it remains CO2 gas.) Fish "breathe" by running water across their gills thereby capturing the O2 dissolved in the water, hence the bubbling of a fish tank.

The solubility of the three gases in water at 1 atm of pressure:

Oxygen
34.1 ml/liter

Nitrogen
16.9 ml/liter

Carbon dioxide
1019.0 ml/liter


Note that N2 has a low solubility as compared with CO2. N2 and CO2 both play a role in the head of beers dispensed with mixed gas. N2 molecules and hence the bubbles are very small compared with CO2, therefore they provide a "creaminess". The mix needs to be right or due to the Law of Partial Pressures your beer will taste flat, i.e. there's not enough CO2 in your beer even though the absolute pressure is high. The solubility of N2 is low and the bubbles are small, which results in a flat beer. The right mix depends on what type of beer you're dispensing and what would be proper for the style. By the way, those really, really tiny bubbles present in a European-style lager, which has been aged for four to six weeks at -1 degrees C, come from the fact that yeast have excreted them (smaller bubbles than any stone) and that the solubility of CO2 in beer increases as the temperature decreases.

For more genereal info on gas pressure, see the following:

http://members.aol.com/profchm/dalton.html

http://www.chm.davidson.edu/ChemistryApplets/GasLaws/DaltonsLaw.html

This site specifically handles the topic of Dalton's Law and beer dispensing:

http://www.sinc.sunysb.edu/Stu/tross/

(The disclaimer at the top is sad, though.)

[Sir Brewsalot]

Crassbrauer,
Are you suggesting (among other things here) that O2 does not react with beer? How about Oxidized beer?....Anyone? Am I reading something wrong or missing something else here?

I'd also offer that the solubility figures quoted are for Standard Temp and Pressure.

Rob,
Before you go out and spend big bucks on a nitro system, take your regular stout, carbonate it (that's w/ CO2 by the way) to between 1.5 and 2.0 volumes, and serve it with nitro on that nitro faucet - straight from your serving tank. Play with the restrictor disk sizes (or removing them completely) to get the best results. If it doesn't work, you've spent nothing and you can still serve the beer on regular CO2 draft.

I've got draft accounts running my regular kegged beer (without nitro) on a nitro spigot, no problem.

Mr. Jay,
We're not getting any closer to an answer for you. That's probably because all we know is what we BELIEVE we know, based on our experience. You can probably dig up the theory here or elsewhere, but that always varies from actual experience...which in my opinion is of more value if you're trying to have a similar experience of your own.

Cheers,
Scott

[pennbrew2]

By the way, those really, really tiny bubbles present in a European-style lager, which has been aged for four to six weeks at -1 degrees C, come from the fact that yeast have excreted them (smaller bubbles than any stone)

You had me up to here. Dissolved CO2 is dissolved CO2, whether from the yeast or from a stone.

---Guy

[crassbrauer]

Sir Brewsalot:
I didn't go into oxidation, which of course also occurs when beer meets oxygen (aka "the brewer's worst enemy"). Oxidation is a chemical reaction. Burning is an extreme example of oxidation, but it also occurs at lower temperatures, in fact, this is one argument for not using pure O2 when aerating wort, because the oxygen dissolves in the beer but also reacts with the anti-oxidants (from the malt and hops) shortening the shelf-life of the beer. Compounds in the beer become oxidized when it is exposed to air. Oxygen dissolved in beer is available for yeast reproduction, whereas oxygen in oxidized compounds is not.

Pennbrew2:
If CO2 is released by yeast in tiny amounts over time at low temperatures, it is very evenly dissolved in the beer. Yes, I guess this could be achieved with a stone but rarely is because carbonating with a stone is used as the "fast" method of carbonation, and the proper times and temperatures aren't generally allowed for really fine carbonation to occur. Perhaps try aging a lager for one, three and five weeks at between 1 and -1 (after allowing the young beer to mature with Kraeusen and new yeast). The carbonation becomes finer and more evenly distributed in smaller bubbles, known as "lace". The yeast conveniently release the CO2 in tiny amounts which facilitates this to a large degree.

[Mad-Brewer]

Carbonation Fairy Tales

Crassbrauer: "The carbonation becomes finer and more evenly distributed in smaller bubbles, known as "lace". The yeast conveniently release the CO2 in tiny amounts which facilitates this to a large degree."

I had to change the title. Things are getting silly here. CO2 in solution canmot trace its roots to a stone or yeast cell and thereby act differently in forming small or large bubbles. Lacing has nothing whatever to do with yeast excreation, but the mix of proteins and complex molecules in solution.

[gitchegumee]

I'm going to side with Crassbrauer and the majority of European brewers that I've met that say that naturally carbonated beer is definitely superior in carbonation to those beers force carbonated. Superior means that the bubbles are tinier, the lacing better, and the taste more refined. Now I'm not sure how that works, and it sure seems counter-intuitive. But it happens. There are many stranger things that happen in the brewhouse & cellar that also cannot be explained well. And carbonation is not that clear-cut and straightforward as you might think. There are dozens of beer scientists out there working on the finer points of bubble formation, retention, protein complexing, gas dynamics, surface tension, physical chemistry, etc. We don't know all there is to know about beer carbonation.

[Mad-Brewer]

Carbonation Fairy Tales

I have personally done side-by-side packing of both force carbonated beer and bottle conditioned beer (same batch, just packing differs) and nobody can tell which is which by quality of head or lacing. As I suggest, and as has been noted, there are dozens of factors which could account for these aspects of a beer in a scientific way, such as ingredients, and mashing techniques. Why turn to some aspect which has no reasonable connection, or explain how a CO2 molecule could possibly know its source. I find an appeal to unscientific reasons poor form for a professional discussion

[jhuck]

And I'm going to have to side with Mad-Brewer on this one. Speaking of yeast producing "bubbles" is misleading. In a closed, presurized system (like a keg) there are no "bubbles" at all. The bubbles form when a pressure difference is introduced in the system, such as opening a small hole at the end of the faucet. Before that, there are only disolved gases, and given enough time those gases will distribute evenly and be indistinguishable.

I agree we've gotten a bit silly in this thread... I think the original posters question has been answered in spades at this point.

[crassbrauer]

OK, one last word...

There’s nothing unscientific or unprofessional about what I’ve written in this thread so far, in fact it’s all very well documented and most of it is basic physics. The only sentence in my original post which seems to have been the cause of further discussion is the one about bubble size and “lace” in bottom-fermented beer, which has been lagered for four weeks or more. More on that subject:

Of course, a CO2 molecule doesn’t know whether it was excreted by yeast or not. That’s not the issue. The issue is how it’s done. In reply to another post: Yes, dissolved CO2 is dissolved CO2, if the CO2 is homogenously distributed throughout the beer. Yeast produce CO2 slowly and in tiny amounts while in suspension throughout the entire volume of the beer. (Yes, actual perceptible bubbles don't appear until the pressure goes below the equilibrium pressure.) Therefore, the yeast taken as a whole possess a huge surface area. A carbonating stone, if it’s a good one, will possess an average pore size of less than 1 micron. However, the surface area of the carbonating stone stuck in on one side at the bottom of the bright tank can’t begin to approach the surface area of the yeast. The tiny amounts of CO2 being released by the yeast throughout the entire volume of the beer facilitate the CO2 going very evenly into solution, i.e. the CO2 has maximum contact with the beer. If that weren’t the case, then it’d be fine just to put a lot of head pressure on the tank and let the beer become carbonated that way, instead of using a carbonating stone, which is an attempt to do what the yeast do. To overcome the surface area problem, it has been suggested that carbonation should be done in-line between the filter and the bright tank.

Additionally, carbonating stones aren’t often “used” the same way yeast are. Yeast release CO2 much more slowly over time during the process of maturation than can commonly be achieved with a carbonating stone. The rate at which the CO2 is released, and that it is done while the other processes of maturation are taking place are important factors to consider. With artificial carbonation, it sometimes happens that CO2 already in solution is ripped out of solution by the bubbles passing through the beer emanating from a carbonating stone which is set too high (or even worse, without a stone, just a hose). Pore size becomes irrelevant at that point. Whether the beer just needs “topping up” or needs a lot of CO2 added to it, also plays a role. Obviously, I’ve had beers with a nice head, carbonated using stones; I wouldn’t argue that point. However, as is often the case, carbonating stones aren’t commonly used like they should be, i.e. not enough time is taken at a low enough temperature to properly carbonate the beer. Rather than yeast vs. carbonating stones, perhaps the real issue is that artificial carbonation is often done incorrectly.

As you mentioned, of course, many other factors play a role in carbonation and head formation in beer. The discussion was originally about gas in beer and not all of the factors contributing to head formation, which is why I didn’t feel the need to comment on them. There are several thousand substances in beer, all of which contribute to its wonderful complexity. Would any of us be interested in these discussions, if the subject were carbonated water? I think not. Does anyone completely understand all of the interactions among the thousands of substances? No, absolutely not. Gushing, a weird facet of carbonation, is a good example. No one yet knows exactly how/why it occurs in every case (on the table: Ca-oxalate, fusarium and other fungi, bad glass, etc.). Research is ongoing. Gitchegumee is right about the complexity of this issue.

Your experiment with the same beer is a valuable contribution to the discussion. It is valuable especially because it dealt with the same beer with and without natural carbonation. It may not be able to be taken as the gospel truth on the subject, since it was performed once and there are some unknowns. I must say, however, it’s definitely better than just taking someone’s word for it and not doing anything.

I was originally specifically referring to bottom-fermented beers, which are lagered for many weeks. Ales are another animal, most of which aren’t aged for nearly as long and often are artifically carbonated. Also, I would never maintain that a naturally carbonated lager would taste perceptibly different from a artificially carbonated one, if it were transported in a shaky, hot truck across three states or otherwise poorly handled. Naturally carbonated lagers have been given the time to mature properly and this, of course, also plays a large role in their overall perception. Lagers that are artificially carbonated sometimes aren’t given the time to mature like they should. This is part of the advantage that small breweries and brew pubs have over others who don’t have this luxury. I’ve been to a lot of small breweries in Bavaria where the beer is still brewed very traditionally with long maturing and lagering times (often left unfiltered) and is only delivered within a 30 km radius of the brewery. The foam on the beers from some of these breweries is pretty amazing. I haven’t really seen it achieved in many other places. Does anyone know every factor responsible for this? I don’t think so.

Beer foam is a huge topic, but I’ve included an extremely brief rundown, so that we’re all on the same page:

Foam consists of CO2 along with some air bubbles (and N2 if applicable). A film exists around each bubble. Some substances in the beer contribute to strengthening this film, others don’t. Foam dissipates because the liquid drains out of the space between the bubbles, and the bubbles coalesce, get bigger, then burst. A higher viscosity (contributing to the elasticity) and smaller bubble diameter result in better head retention, because the liquid flows more slowly out of the matrix formed by the bubbles. (This is where the N2 can help.)

Factors affecting head retention:
1. Barley: Amount and type of protein
2. Malt: If it’s too highly modified, there are not enough high molecular weight proteins for good head retention. There’s no correlation between β-glucans and foam, as previously thought.
3. Mashing: A protein rest may contribute or detract from head retention depending upon the malt. Beware of lipases; avoid their optima. Parameters: time, temperature and pH.
4. Lautering: Too many wort solids result in bad foam (fatty acids, etc.)
5. Hops: Type of hops and the time they’re added affect foam. Some bittering substances contribute to head retention.
5. Boiling: Coagulable protein is important for foam. Some Maillard products are positive for foam.
6. Fermentation: Yeast nutrients are important. There is a direct correlation between yeast vitality and foam stability. Some brewers put in more yeast to make up for the fact that their yeast are unhealthy. These yeast release substances which kill foam (bad fermentation/unhealthy yeast = bad foam).
7. Maturation and Lagering: The maturation and lagering of a beer for too long or at too high a temperature is negative for foam, because the yeast can excrete alkaline amino acids, fatty acids and enzymes.
8. Filtering: How it’s done, to what degree and with what materials affect the substances which in turn affect foam stability.
9. Packaging: Temperature, good glass (see cleansers and sanitizers)
10. Cleaners and Sanitizers: If used improperly, the surface tension of the beer can decrease and therefore foam retention as well.
11. Other: Alginate, enzymes, etc. can be added to improve foam stability.

[BMOOR]

carbonating with head pressure

I've enjoyed this thread as it's a topic we can all learn from.
I'm sure that crassbrauer knows a lot more about this topic than I so I have not tried to "choose a side". Also, it's starting to look like a beat up crassbrauer party(call me a nice guy. I guess), but your quote:

The tiny amounts of CO2 being released by the yeast throughout the entire volume of the beer facilitate the CO2 going very evenly into solution, i.e. the CO2 has maximum contact with the beer. If that weren’t the case, then it’d be fine just to put a lot of head pressure on the tank and let the beer become carbonated that way, instead of using a carbonating stone, which is an attempt to do what the yeast do.

natural carbonation probably does facilitate CO2 going in more evenly than stones and more so than head pressuree, but I wouldn't say it's "not fine to just add head pressure to carbonate". We do that with every beer and it has worked fine. Sure, it takes another week after fully fermented and crashed, but I can take 15bbl of beer with zero volumes of gas to 2.3 volumes in about a week by adding 16-17 psi each day and letting it dissolve.

IF I misread you, I apologize, just letting people know that it can be done easily and effectively.

Thanks all for adding some science into the discussion rather than just opinions.
Cheers!