Thursday, May 9, 2013

The myth of nitro beer.

I like "nitro" beers. I especially like English style bitters on "nitro". A couple of years ago Left Hand Sawtooth Ale started showing up around town being dispensed from nitro spouts. Sometimes the pub simply delivered a standard keg of Sawtooth using nitro gas and spout, which is ok but not that special, but sometimes I come across a Nitro Sawtooth that tastes like it was meant for nitro delivery. By that I mean that the beer is delivered with a relatively low amount of carbonation and a nice creamy head. The nitro sawtooth quickly became my beer of choice, over even my own homebrewed bitters; it was time for action.

Last summer I took the plunge and invested in a nitro system for my upstairs kegerator. This meant acquiring a nitrogen tank and regulator for the gas, two new nitro spouts, and the lines and hardware to connect it all up. I hooked it up and started experimenting with methods of conditioning the beer for service via nitro taps. Through reading, I had learned that nitrogen isn't soluble in beer, so the initial conditioning needs to be done via co2. The strategy was to carbonate the beer to a low pressure with co2 and then serve the beer using higher pressure using beer gas (75% nitro / 25% co2). After a couple of kegs, I got my conditioning figured out and my beer was serving nicely. I carbonate to about 7lbs and would set the beer gas to about 30 lbs.

It all worked pretty well, but I didn't quite understand what it was I liked so much. I had heard and had myself exclaimed that "nitro has smaller bubbles" which contributes to the creaminess. Nitro supposedly makes the beer closer to REAL ale. Nitro.. nitro.. nitro.... The whole "non-soluble" concept bugged me, though. If the nitro didn't dissolve into the beer then how did it get dispensed into the head. What was the point. There must be some mis-information or some magic going on.

This past weekend, we had some friends over to help drink some beer, and my nitro tank ran out about halfway through the evening (I'm thinking my system has a slow leak that is exploited by the high pressure of the nitro tank - but that is for another discussion). Not wanting to put an end to the consumption of those beers, I hooked up my spare co2 tank to those kegs and kept them pouring. I was a little worried about their mouthfeel or how the pour would be without the nitro, but my initial test was fine so I didn't think much more about it that night. People kept drinking it without any negative comments.

A few days later I was curious and decided to check out the beer situation for myself. Again, there seemed to be no major difference from nitro to co2. I was still pouring through the nitro spouts, and the pour was a little slow, but the signature cascade was still there, the thick creamy head was still there, and the beer was still lightly carbonated and smooth to drink. So I went back to read more about it on the internets. There doesn't appear to be a single definitive source of information about serving beer on nitro, but what follows are my conclusions:

  • Nitro beer is smooth because of low carbonation.
  • The nitro creamy head and cascade are a result of the nitro spout and the creamer plate inside that spout. (Perhaps a creamer adapter for a standard stout would do the same thing? I have never used one.)
  • Many pubs have taps that are quite a distance form the kegs, requiring higher pressure to push the beer to the taps and to serve the beer(both for standard and for nitro taps).
  • Beer gas (nitro/co2 mix) allows for higher pressure between the keg and the tap without the danger of increasing the carbonation of the beer.
So it would appear that really the only thing beer gas does for a nitro system is push the beer to and through the tap without changing the carb level. And perhaps the higher pressure helps dispense the beer faster (though with the settling time required for nitro beers does that really matter?). Therefore most homebrewers (and anyone else whose tap is situated in close proximity to the keg) do not actually need to serve the beer using beer gas. Simply carbonate the beer to the desired lower carbonation level and serve that beer at that same pressure. As long as that is enough pressure to push the beer through the spout and its creamer plate, then the final product will be same. At least in my experience this is how it works.  I will be doing further experimentation (with fresh kegs) to test this theory.

(This "theory" has other corollary observations. For one, Left Hand bottles their "nitro" milk stout without a widget or any other obvious bottle addition. Their strategy for creating the cream head and nitro experience is to "pour hard". Anyone who has poured normal beer knows that a hard pour will cause the beer to foam much more than a gentle pour down the side of the glass. Well.. perhaps by filling that bottle with low-carbonated beer, a "hard pour" will cause the limited carbonation to foam up as desired. I poured my first ever bottle of Nitro™ Milk Stout before seeing the "pour hard" instructions and poured it like any other beer, which created essentially no foam, but it was still a low-carbonated beer. A hard pour, on the other hand, did produce more of the desired effect. So I ask you, gimmick? Why don't they call it a low-carb(onation) beer instead of "nitro"?)

I'm not sure there really is such a thing as nitro beer. Only nitro delivered beer. (The exception being Guiness and its British cousins, which really are served with nitrogen that is released from a widget. There is no need to "pour hard" with a Guiness as the nitrogen really is dispensed with the beer and appears to generate the head. Or maybe that really is magic.) Of course, I could be wrong.

Anyone want to buy a nitro tank and regulator?

Edit: For the record, I went home tonight and reminded myself about the pouring/drinking experience of the Left Hand Nitro™ Milk Stout, and it may just have some nitrogen in the bottle. The "pour hard" dispensing did produce a slow cascade effect reminiscent of a nitro spout pour. So somehow they managed to hide some nitro in the beer during the bottling process.  I'm still not convinced, however, that serving a beer on nitro does anything but deliver with higher pressure without over-carbonating the beer.


Michael Papile said...

You are right about this. Nitrogen does not enter the beer in any appreciable quantity. It is used with 25% CO2 to keep the carbonation while forcing the beer through the restrictor plate in the stout faucet. It was originally devised to simulate the pump pour of cask ales in the UK which is at high pressure.

WatchAndPray said...

So how much pressure is actually needed to push the beer through the nitro tap using co2? Thanks!

Troy said...

I typically run it at about 7psi. It is a slower pour, but a much cheaper pour; and it still has the cascade and smooth mouthfeel.

Infinity Racing said...

I had a similar thought. I was reading a BYO article where a person asked if it was possible to bottle a nitro beer from the tap. The person said that it wasn't possible and explain how nitro taps work by forcing the beer through a plate with tiny holes. If Left hand can bottle without a widget and nitrogen isn't soluble in beer then it has to be largely about how the beer is poured as there is nothing special about the bottle that's used. I am going to try and pour an under-carbonated homebrew tonight like this!

Given all the time/money LH put into making the nitro bottle work I can't image that it's actually as simple as this. Maybe LH spent tons of time researching different methods and ended up realizing that it is a lot more simple than imagined (but of course they wouldn't tell anyone that).

A more likely explanation could be that they bottle the beer with a certain mix of Nitrogen/CO2 gas. The low CO2 % would cause the low carbonation level while the nitrogen gas would cause more pressure in the head space therefore giving the impression that it's a normally carbonated beer. Since nitrogen is heavier than CO2, a good amount of the nitrogen would stay in the head space when the bottle is opened.Finally, the magic all happens in the hard pour. Without the hard pour you'd just be left with under carbonated beer. The turbulence caused by the hard pour could also cause the nitrogen in the head space to temporarily mix with the beer that flows out of the bottle.