Process for Charmat Method Sparkling in a Keg

[JustinTG]

Hi all, I’m wondering if there is a “definitive guide” to doing a Charmat method sparkling wine in a keg. We’ve been bottle carbing (no disgorging though) but want to try the Charmat method. At the highest level, I think some of the steps are:

I. Make a clear base wine and transfer to keg.
II. Add sugar yeast mixture
III. Seal
IV. Wait ~ 7 weeks
V. Bottle

Sounds simple but I have a ton of questions. For example:

1) What are the pros and cons of doing this in a commercial keg versus a corny keg (I just learned there was a difference)? The corny kegs are easier but are they less suitable for the pressure?

2) How high can I fill the keg? Can I top it off like I do when doing sparkling in the traditional method?

3) What is the best way to seal the keg? Do you need a pressure gauge or can you just seal the thing up?

4) How much pressure will these kegs withstand? Are there standard ratings? What about things like gaskets?

5) I see that brewers bottle from a keg with a “counter-pressure” filler. Would that work here? Is it as simple as hooking up a hose to the keg and the counter-pressure filler to the host to bottle?

6) Do I still need to use champagne bottles? My physics-delinquent brain tells me that pressure won’t build in the bottle because the fermentation is done. But maybe that’s wrong?

7) Any strategies for dealing with the sediment? Since kegs are tapped from the top, will the sediment stay at the bottom?



These questions are just to add some specificity but I am looking for any general insights and experiences. Thanks all.

 

[BarrelMonkey]

I've only ever done bottle carbonation (traditional/champagne method) but to address some of your points:

1) What are the pros and cons of doing this in a commercial keg versus a corny keg (I just learned there was a difference)? The corny kegs are easier but are they less suitable for the pressure?

2) How high can I fill the keg? Can I top it off like I do when doing sparkling in the traditional method?

3) What is the best way to seal the keg? Do you need a pressure gauge or can you just seal the thing up?

4) How much pressure will these kegs withstand? Are there standard ratings? What about things like gaskets?

A quick Google search suggests that kegs are typically rated to 60psi. This is fine for most beers but not sufficient for sparkling wine. Champagne can get to over 6 atm, which is ~90psi.

Bottom line: Do NOT do this in a keg unless it's a real pressure vessel specifically designed to withstand high pressure. Even if your fermentation goes off successfully, you have to somehow get the (highly pressurized) wine out of the keg and into bottle. How are you going to get the cap off? I've opened several pressurized kegs in my time (not from making sparkling wine, but accidentally pressurized eg if a supposedly finished wine starts to referment). It's very dangerous. (If you have to do this you need to press down hard on the cap with one hand and carefully remove the clamp. Gently release pressure with your hand and let the gas escape as slowly as possible. Beware that the cap may get stuck onto the keg via the gasket, in which case do not leave it like this unattended. The cap can fly off with great force and cause serious injury).

6) Do I still need to use champagne bottles? My physics-delinquent brain tells me that pressure won’t build in the bottle because the fermentation is done. But maybe that’s wrong?

Yes, you absolutely still need to use champagne bottles. The pressure comes from dissolved CO2 which will still be largely there when you bottle the wine. You may lose ~5% of the pressure in a champagne bottle at disgorging, but most of it is still there when you put the final cork/cap in place. Again, these sorts of pressures are no joke. We always wear long sleeves, eye protection and cut resistant gloves when handling non-disgorged sparkling bottles and working on the disgorging line since accidents can happen even under well controlled conditions.

7) Any strategies for dealing with the sediment? Since kegs are tapped from the top, will the sediment stay at the bottom?

Charmat process wines are typically filtered; I assume this needs to be done in some sort of pressure-rated system but I've never done it.

 

[JustinTG]

Thanks for all of the info!

I certainly understand we don't want to exceed the pressure rating of a keg, but I'd be ok (at least for experiment's sake) only getting about 30 PSI. I think beer kegs are designed to withstand pressure (please correct me if that's not right) so as long as we does to remain comfortable under the pressure rating, we should mitigate a lot of the risk. Please let me know if I'm missing something.

How are you going to get the cap off?

I wasn't thinking about removing the cap. I was more thinking about hooking the keg up to a tap and then attaching a counter-pressure bottle filler. There are a ton of videos on how to do this with beer (e.g. ) and I figured the mechanics would be the same for sparkling, of course provided the pressure was low enough that nothing broke. It's a shot in the dark though and maybe there is something I am unaware of that makes the processes different.

and working on the disgorging line

I assume you mean with commercial equipment, right? If you are doing this at home, I'd be curious to your method. I've heard of the dry ice, water and rock salt, "bubble" method and a bunch of other hacks but I'm not quite convinced that I'd be able to pull those off.

 

[BarrelMonkey]

Thanks for all of the info!

I certainly understand we don't want to exceed the pressure rating of a keg, but I'd be ok (at least for experiment's sake) only getting about 30 PSI. I think beer kegs are designed to withstand pressure (please correct me if that's not right)

From what I read, kegs are built to withstand 60psi - google 'keg pressure rating' or something smilar. There should be a pressure rating engraved on the keg. I think most beers are carbonated at around 15psi.

I assume you mean with commercial equipment, right? If you are doing this at home, I'd be curious to your method. I've heard of the dry ice, water and rock salt, "bubble" method and a bunch of other hacks but I'm not quite convinced that I'd be able to pull those off.

I've used a commercial disgorging line but also done it at home - see here. The riddling rack is nice to have if you're disgorging a couple of cases, but you can also just 'kick riddle', ie put the bottles in a wine box with caps down and give it a kick/shake every day for a week or two, then settle for a few days before disgorging.

The 'bubble' method (a la volee) does take some practice but if you use the freezing method (a la glacee) with either dry ice or rock salt/ice, it can be quite reliable. Give it a go!

 

[Rice_Guy]

We have two members of Prairie vinters who will use, brag on, glycol (antifreeze) in a freezer. I have not seen details on their sparkling wines.
If I am using pressure equipment in the pilot plant I will ALWAYS have a high pressure relief valve. ,, Have you looked at beer related pressure relief valves? Relief valves are standard anyplace one deals with pressure whether on a canning kettle / retort or even a water heater. What I have done with soda starts with low temp liquids, what are your process details?

, , , Sometime with the new crop I am going get a SPUNDING valve and set up a 5 gal SS keg for fermentation. Pressure fermentation is doable. ,,, If I am to believe the concept as used in beer it allows warmer temps with better flavor control.

 

[BarrelMonkey]

We have two members of Prairie vinters who will use, brag on, glycol (antifreeze) in a freezer.

Just to be clear - the antifreeze that you put in your car radiator is ethylene glycol which is quite poisonous. Food grade glycol is propylene glycol (though even then make sure it is food grade and not for industrial use). Typically, commercial neck freezers use a mix of propylene glycol and water. It's a good option - more expensive than ice/rock salt though it can be saved and reused.

 

[JustinTG]

Thanks @BarrelMonkey, I'm now inspired to try a la glacee (thanks for the vocab too). Your setup looks nice. Also I am seeing some Corny kegs (according to the people that are selling them of course) rated up to 80 PSI. That should be plenty of room if I'm going to shoot for 30 PSI.

@Rice_Guy you are right. As I was doing more reading, most kegs have pressure release valves. Furthermore, I also just started reading about Spunding Valves (which is kind of like a pressure release valve with a customizable release pressure if I understand correctly.

So it looks like keg rated to 80 PSI and aiming for a 30-40 PSI and using a spunding valve should mitigate most of the safety risks.

Any experience with bottling under pressure? The counter pressure filler is all I can find but maybe there are other options.

 

[Raptor99]

I have several Corny kegs and a kegerator that I use for hard cider. I think that most Corny kegs are rated at 60 psi, although this one is rated 130 psi: https://cornykeg.com/products/239

If you are satisfied with a beer-level carbonation, then a keg would work well. The solubility of CO2 in liquid increases as the temperature drops, so if you keep your keg around 32 degrees F you will the the maximum amount of carbonation at a given pressure.

For ciders, 12 psi provides enough carbonation for me. For a sparking wine, I would go higher. 50 psi would provide a lot of carbonation at ~ 35 degrees F

The beer forums discuss several different methods of bottling from a keg. If you do that, keep in mind that as the temperature goes up, the liquid will hold less CO2, so the pressure will rise.

Here is a table designed for beer: https://www.kegerators.com/carbonation-table/ The amount of CO2 in a carbonated beverage is usually measured in "volumes" of CO2, which is defined as liters CO2/L beer) at standard temperature and pressure. In other words, 3 volumes mean enough CO2 to fill the bottle 3x at roughly room temperature. Sparkling wine is usually carbonated to 4-6 volumes of CO2.

If you want 3 volumes, you can get that with 12 psi at 30 degrees F. If you raise the temp to 58 degrees F, that becomes 30 psi. If you have 5 volumes CO2. The chart does not go high enough to give the pressure of 5 volumes of CO2 at room temperature. As you raise the temperature, the psi can increase by 3x or more. That means that if you want to store the bottles at room temperature, they need to be able to withstand a much higher pressure. But you need a much lower pressure in your keg at a lower temperature. At 30 degrees F, 29 psi will give you 5 volumes of CO2. You also need to be careful if you take the keg out of the kegerator, because the pressure will increase.

Short answer: you can use a keg as long as you keep it cold. Be sure your bottles can withstand the increased pressure at room temperature.