Force Carbonation of Kegs

[BevMan]

I have a few 50litre kegs to be carbonated by hand. I have read a lot about temperature and cooling the beer down to allow CO2 to be absorbed and this is certainly the advice given to hombrewers but in every instance I have seen they keep the keg in a fridge after carbonating.

My questions are :

1. Does it need to be done at a low temp ? Naturally carbonated kegs and bottles arent.

2. If it is done at a low temp and the keg is allowed to reach room temp, does the CO2 release from the beer and go into headspace ? Wouldnt the same apply to bottles ?

3. I have seen commercial kegs served at room temp through an ice box and they have normal head etc. Is there a difference in the process that these kegs go through ?

4. Any suggestions greatly appreciated. I have found my attempts so far at normal temp have not carbonated sufficiently and I am concerned about carbonating at low temp then transporting and/or serving from a keg at room temp.

Thanks in advance

[David Quinn]

I too have seen #3

A keg of Newcastle on tap at a small seafood restaurant in coastal SC, run through an ice box to chill the beer at the time of serving. Let me just say this was perhaps the worst beer I have ever tasted that wasnt obviously infected and dont recommend the process to anyone.

Sorry I cant offer any scientific advice on your other points, but it seems that the low temp allows CO2 to be absorbed, and as long as the system is pressurized/sealed, then the gass should stay in solution. I would think if you carbonated at say 36F properly and let the keg warm up, the pressure of the head space would be higher, but the CO2 (most of it anyway) should still be in solution. So therefore, you could let a keg warm up, but would want to chill it before serving or else you might pour all foam all the time.

Just speculating.

[GlacierBrewing]

I'm assuming you are not utilizing yeast in solution to create the carbonation. Having said that, I have had great success connecting a CO2 line to the keg via a Sanke keg fitting. However, I configure the keg fitting with the CO2 line injecting down the main keg spear (where the beer usually flows out from). I keep the keg cold. You should be able to find the carbonation chart in any good homebrew/brewing book. It's a relationship of CO2 pressure and beer temperature: the colder the beer (to a point) the quicker the CO2 will go into solution (I know these are not exact but something like 19psi at 34degrees F for 1-2 days = VCO2 ~ 2.8 volumes). Like any beer, if it warms up and the pressure is removed (i.e. pouring a pint!), the CO2 will come out of solution VERY rapidly. Keep the keg COLD and under PRESSURE! Hope this helps.

Luck to ya'
Dave

[jipjanneke]

Both the above guys have the right clues.

Scienfically, the partial pressure of most gases varies proportionally with temperature. This means that the 'desire' of the gas (e.g. CO2) to be in the gas phase compared with the liquid phase or dissolved in another liquid (e.g. beer) increases as the temperature rises. The higher the temperature, the more energy the gas molecules have to push themselves into their phase of preference (i.e. gas). We see this as an increase in pressure in a sealed container (e.g. keg) which heats up which was originally pressured and capped whilst cold. When such a keg is tapped, this gas is dying to come out of solution, and so was see foam.

In a closed container, pressure is generated only by whatever is in the gas phase. If the container remains closed, the pressure rises and falls and the temperature rises as falls. The partial pressure of CO2 is the proportional contribution to this pressure of the relative amount of gaseous CO2, but in a beer keg will be the dominant contributor. The other (minor) contributor will include water vapour. Both CO2 and water vapour will follow the temperature/pressure relationship law.

Another thermophysical principle which is of vital important is 'equilibrium'. This refers to the balance reached by the CO2 molecules within the keg to be in either the dissolved or gaseous state. When equilibrium is reached, the number of molecules entering the gasoues state from the dissolved state is equal to the number entering the dissolved state from the gaseous state. This takes TIME. A keg which carbonates naturally can reach equilibrium. A keg which is placed in a coolroom and cools down over a period of several hours or more can reach equilibrium. Beer which passes through an ice box will not reach equilibrium - that is, the aditional CO2 which should be dissolved at the serving temperature will not be dissolved.

A naturally carbonated keg will generate CO2 and dissolve only as much CO2 as it can at the conditioning temperature. The rest will remain as gaseous CO2 in the head space of the keg. When such a keg is placed in a coolroom, more of the gaseous CO2 is dissolved, and the beer goes slightly 'flatter'. This is good - if this beer is tapped and kept cold and under pressure until it is poured, this CO2 remains in solution until the applied pressure is released (e.g. the beer leaves the tap and enters your glass) or the beer heats up (shouldn't happen with a well designed serving system).

However, a keg which is not totally cooled prior to serving cannot dissolve this additional CO2. If it is naturally carbonated at more or less serving temperature, this might be ok (since the serving temp and carbonation temperature are the same). Passing such a beer through an ice box will cool the beer. However, as the pressure falls through the serving lines or across the tap, the CO2 will more easily come out of solution and the beer will be foamier.

If you tap a keg in a coolroom and supply a CO2 line to it, you need to wait until it reaches equilibrium before serving.

So, to answer your questions in light of the aove:

1. Yes, if you want to serve cold, well carbonated beer without too much foam.

2. Yes a little more gas does physicially enter the headspace. We see this as an increase in keg pressure. If, say a keg (or bottle) is naturally carbonated, we would see a ceretain amount of CO2 dissolved and a certain pressure developed. If this conatiner is cooled, the pressure will fall slightly as more gas dissolves; if it warms up again the pressure will return to the original ONLY if this is done in a manner which allows equilibrium to happen (i.e. over several hours, where all of the keg's contants is able to achieve the same temperature; not if beer is passed through an ice box, the keg is shaken, the CO2 supplied to a tapped keg is at a different pressure to the pressure the keg was at before tapping and then immediately served etc).

3. I imagine that only commercial kegs which are carbonated at room temperature would have any chnace of being served without excess foaming. But the gassiness of beer served from these kegs will be very different to that served from kegs which are kept cold in a coolroom and allowed to reach equilibrium. This is probably why you can physically do it but the beer rates crap. Homebrew served in bottles is always served from a cold container, and so will always be carbonated differently (and more along the lines of what we are used to saying is 'good') from, say, a homebrew which is poured from a warm bottle into a cold glass with ice cubes in it! I imagine that the dextrose dosing rate recommended for homebrews is calculated to provide the correct amount of carbonation at serving temperature, not conditioning temperature. 'Correct' is a subjective thing, but we all know what a well served compared with a badly served beer tastes like.

4. If you condition/carbonate at low temperature and then transport this keg to a warm condition, then pass the beer through an ice box, the beer will be very foamy. The additional CO2 dissolved during the low-temp period will be busting to get out at the warmer temperature. Cooling the beer in an ice box will not provide the equilibrium conditions required to redissolve this CO2 back to the original amount.

Hope this helps.

4.

[GlacierBrewing]

yea, what he said!

[tarmadilo]

What he said indeed!!!

Let me add that I briefly carbonated beer in kegs the way you mention, and even carbonating them in a cold room was a difficult and time-consuming process. In fact, if you fill the keg all the way up, it becomes nigh-impossible. You absolutely have to leave a fair amount of headspace, so there's as much surface area available as possible or practical. Otherwise, the beer won't absorb the gas. Having some headspace also helps when you then shake the bejesus out of the kegs, trying to get the gas to absorb...

I'll never go that route again!

Cheers, Tim

[Ted Briggs]

Let me add a few things that may help.
"1. Does it need to be done at a low temp ? Naturally carbonated kegs and bottles arent."
Yes, bottle conditioning is done with a warm phase to PRODUCE Co2 followed by Cold conditioning for Co2 ABSORBTION.

"2. If it is done at a low temp and the keg is allowed to reach room temp, does the CO2 release from the beer and go into headspace ? Wouldnt the same apply to bottles ?"
Yes and yes. As soon as the preassure drops, ie serving, co2 will break out and you have a foamy mess.

"3. I have seen commercial kegs served at room temp through an ice box and they have normal head etc. Is there a difference in the process that these kegs go through ?"
I dont think you have seen what you thought. The kegs were cold and probably had a jacket or were on ice. An Ice box helps by chilling the beer, but warm beer is foamy- period.

"4. Any suggestions greatly appreciated. I have found my attempts so far at normal temp have not carbonated sufficiently and I am concerned about carbonating at low temp then transporting and/or serving from a keg at room temp."
DONT let your beer get warm!! Beer should be treated like milk, ther are both highly perisable beverages. Carbonating in keg is slow but possible. I suggest Karusening with wort or dextrose at the proper level (see handbook of brewing calculations) and aging at room temp for 7-10 days. Note fresh yeast may be nessasary if the beer was filtered or stored cold. Then chill the beer for a week. serve COLD. Just think of the kegs a big bottles......

[David Quinn]

Ted,


Great advice, can you tell me where can I get a hold of the "handbook of brewing calculations" I purchased a laboratory techniques book, and it is somewhat helpful, but this one sounds more like the chemistry manual I need.

[BevMan]

Thanks for the wealth of knowledge - certainly the best place to be for pro brewers and more in depth discussion I still have to go over many of the suggestions.

Ted - in point 3 warm kegs - I have poured beer from kegs at room temp through an ice box and know of a few places that do it. Beer must be used quickly as it is at ambient temp but it poors pretty well as it should and I have heard that commercial breweries do something different or process the beer differently as opposed to say a home brewer force carbonating and needing to serve from a chilled keg.

The other point about freshness is that home brewers beer is better after a long maturation of even a few months. Not sure if the same can be said about kegs but I have a few soda kegs that have been stored for a while that I am going to crack open and check. When a commercial keg is not chilled it must be consumed quickly. Hombrewers dont use preservatives so what is the difference ?

Thanks

[David Quinn]

When refering to "commercial breweries" you mean those that filter AND pasteurize their beer?

I have heard that a filtered product can take a warming if it was pasteurized, and so can an unfiltered/unpasteurized beer, but a beer that has been filtered and NOT pasteurized must be kept cold or risk spoiling.

Any thoughts?

Nothing like moving slightly off topic eh?

[tarmadilo]

Homebrewers certainly do use a very powerful preservative....hops!

As far as I know, commercial draft beer is almost never pasteurized. In fact, both Coors and Miller bragged about their canned beer being "cold filtered" like kegged beer and not pasteurized, and Miller even calls that beer "Genuine Draft".

You may have seen kegs sitting out unrefrigerated, run through a cold box, but I'd wager that beer was stored cold right up to the point when they had to tap it. It takes 15.5 gallons of beer quite a while to heat up, so for a while at least, that beer oughta be okay.

Beer shouldn't be stored or served at room temperature. It won't taste as good or hold its carbonation right. It's perishable food!

Cheers, Tim

[jipjanneke]

There is already a topic thread regarding the 'aging' and storage of commercial/homebrews on this forum which you may wish to also refer to:

http://www.probrewer.com/vbulletin/s...&threadid=1605

[tarmadilo]

Hey, I thought I was the one who was supposed to link to previous discussions!!!

Nice save!

Cheers, Tim

[gitchegumee]

Draft beer is frequently served from a warm keg. We used ice chests with coils or plates to cool the beer as it was poured. They are commonly used where there is no access to electricity and where the climate is warm. The long coils ensure that the beer has lots of restriction as the CO2 pressure must be kept very high to maintain the correct carbonation. And for that reason, the beer should never start out chilled and allowed to warm--you would have to constantly adjust the pressure. IMHO, beer dispensed properly this way is indistinguishable from beer served from a cold box. In Korea, draft beer is not transported, stored, or kept on tap chilled. Everything is ambient and served through a chiller. Likewise in Japan where last weekend's Great Japan Beer Festival saw all draft beer stored warm and served through plate chillers. One major disadvantage to this method is that the beer is more prone to bacteria spoilage.

[Ted]

I, too, am familiar with Asia and just knew somebody was going to bring up the flash chillers with the ice banks. Those are used exclusively (except the brewpubs I put in) in China and Taiwan. I have not had the greatest success unless the beer is micro-filtered (.4um), though. Your basic microbrew will not perfrom well under these circumstances. I had one instance in Hong Kong where a customer asked why there was so much foam only to discover he had moved the keg from behind a tight bar to a spacious location out a window on a tar roof. It had to be 2,000 degrees out there. The beer was slightly (nudge, nudge) shall we say...off.