Need Help With Nitro Kegging Info

[MetalMike144K]

Need experienced users of nitro kegging for
info.

All of the nitrogen tap setups online with the bottle, regulator and stout tap are extremely vague about the actual nitrogenating of the beer in their guides and info to setting up Nitro kegging.

Most of the systems just simply say to carbonate to about 1 to 1.5 volumes with CO2 and then simply hook up the beer gas mix and start serving through the Stout tap right away. If the beer gas is simply pushing the beer through the top of the keg (like normal CO2) the beer coming out at first is really not getting nitrogenated at all.

Just being forced through the restrictor plate I assume. Some places online do say to drop a stone and line into the keg and gas the beer for 30 minutes, a 30 minute chill break and then another 30 minutes of gas before serving. I would like full clarification if it's possible.

 

[btbnl]

The nitrogen is insoluble - you're really just using it to push the carbonated beer at high pressure since if you used CO2 you'd over-carbonate. I've even seen people using inert gases (argon, for example) since they had access to it.

The downside to pure N2 (or Ar) is that as the keg empties the absence of new CO2 in the growing headspace means that it comes out of solution in the beer, so you slowly decarbonate. Beer gas uses a mixture of N2 and CO2 (75/25 for example) so that you can use high pressure and keep the right balance between the CO2 in the beer and the headspace.

 

[ajdelange]

The nitrogen is insoluble - you're really just using it to push the carbonated beer at high pressure since if you used CO2 you'd over-carbonate.

The nitrogen is not insoluble. It is just appreciably less soluble than CO2. Some does dissolve in the beer and when the beer comes out of solution considerable Nitrogen is found within the bubbles. This does two things. First, as it is not very soluble in the film that surrounds the bubble it does not diffuse through the bubble as fast as the CO2 does. This means a longer lasting head of tiny bubbles. Second, over time the relative partial pressures of CO2 and N2 change in favor of N2 leading to less acidic and physical 'prick' on the tongue when the bubble bursts. Hence the creamy sensation produced by the head. Thus while part of the job of the N2 is to push the beer through the sparkler plate it also has a very important role as a bubble gas component.

So how much N2 is in your average stout bubble? I have a stout which I carbonated to about an atmosphere of CO2 and then when tapping it placed under 4 atm mix made up of 1 atm CO2 and 3 of N2. Though tapped weeks ago I'm not sure it is yet at equilibrium because I keep forgetting to bleed the head space. Reflection (see below) suggests that bleeding the headspace isn't really necessary, In any case the bubbles now measure 14% N2 which is roughly consistent with calculated values based on temperatures, pressures and the Henry coefficients of the two gasses in water. The details are in another thread (Great Nitrogen Bubble Debate under Brewing Science). The method for measuring N2 content of stout foam is also described there.

The downside to pure N2 (or Ar) is that as the keg empties the absence of new CO2 in the growing headspace means that it comes out of solution in the beer, so you slowly decarbonate. Beer gas uses a mixture of N2 and CO2 (75/25 for example) so that you can use high pressure and keep the right balance between the CO2 in the beer and the headspace.

The proper way to do it is to condition to about 1 volume and then, when ready to serve, put under 3 atm (gauge) 25:75::CO2:N2 mix. The CO2 will be in equilibrium and over the course of a couple of weeks the N2 will dissolve and equilibrium with respect to N2 will be approached so that you get the benefits of N2 in the bubbles. Thus this is the answer for OP. The draws for the first couple of weeks will be CO2 only filled bubble and thus coarser, shorter lived and more prickly than you will find after the N2 has dissolved. You could, of course, put the properly CO2 conditioned beer under 2 atm (gauge) pure nitrogen for a couple of weeks if you want it completely ready to go when tapped.

 

[MetalMike144K]

Thank you both for the replies. ajdelange Thank you for the thorough explanation. So from what I get simplified from your response is that if I do the one volume carbonation and put the beer on the beer gas mix for about 2 to 3 weeks the beer will have enough N2 dissolved to enjoy the benefits of nitrogen. That sounds pretty reasonable. I think locally all I'm going to be able to get is the 75/25 mix.

 

[ajdelange]

That should do it for you.