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Getting rid of CO2 by vaccuum pre-bottling

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Smarrikåka

Smarrikåka

NewBee
Registered Member
Sep 25, 2006
344
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Stockholm, Sweden
www.mjodhamnen.se
Some of you are a little familiar with what I'm doing here in Sweden with the mobile meadery. All the meads we've made so far are great tasting. We're almost exclusively using DV10 as the yeast. Its speed in fermentation in combination with leaving varietal character alone makes it perfect for what we are doing (Making lots of 850 L batches of different products, in a lot of different places with different honeys, and sometimes other ingredients from different beekeepers)

The downside of DV10 is that it takes ages for it to clear. So we have 6 months of maturation to deal with this, and it will clear, but I don't think all the CO2 will clear completely.

In order to deal with that problem, we will have a pre-bottling tank that has a safety-valves that can be set to release at a pressure of your choice (both up and down). We also have a vaccuum pump that can be connected to the top of this tank, in order to clear the air, above the liquid inside it.

The tank has a total volume of 1000 L and is 2,4 m high in total, and expected liquid inside it pre-bottling is expected to be somewhere in the range 800 to 850 L (liquid level height, probably around 1,8m in terms of how it affects pressure), which has been stored in a tank with airlock protected by mineral oil for 6 months post fermentation.

My question is, if the vaccuum pump is used to clear the last of the CO2, what would you reccomend the security pressure valves to be set to, and for how long time should the pump be applied. If the goal is to get rid of the CO2, while trying to preserve aroma to as great a degree as possible?
 
Smarrikåka said:
Some of you are a little familiar with what I'm doing here in Sweden with the mobile meadery. All the meads we've made so far are great tasting. We're almost exclusively using DV10 as the yeast. Its speed in fermentation in combination with leaving varietal character alone makes it perfect for what we are doing (Making lots of 850 L batches of different products, in a lot of different places with different honeys, and sometimes other ingredients from different beekeepers)

The downside of DV10 is that it takes ages for it to clear. So we have 6 months of maturation to deal with this, and it will clear, but I don't think all the CO2 will clear completely.

In order to deal with that problem, we will have a pre-bottling tank that has a safety-valves that can be set to release at a pressure of your choice (both up and down). We also have a vaccuum pump that can be connected to the top of this tank, in order to clear the air, above the liquid inside it.

The tank has a total volume of 1000 L and is 2,4 m high in total, and expected liquid inside it pre-bottling is expected to be somewhere in the range 800 to 850 L (liquid level height, probably around 1,8m in terms of how it affects pressure), which has been stored in a tank with airlock protected by mineral oil for 6 months post fermentation.

My question is, if the vaccuum pump is used to clear the last of the CO2, what would you reccomend the security pressure valves to be set to, and for how long time should the pump be applied. If the goal is to get rid of the CO2, while trying to preserve aroma to as great a degree as possible?
Click to expand...
Hum? Well, apparently the enolmatic vacuum bottler draws about 28 to 29 inches of mercury, and with slight modification (factory modification that is) it can be used for de-gassing and racking.

While it only needs about 10 inches of mercury to rack the liquid, for de-gassing, it can be plugged into a fermenter (up to about 50 or so litres - not 1000l ones) and it seems that the 28/29 inches of mercury that the pump is capable of, is fine (for fine, think "safe"). I'd guess it can be set on the lowest amount of vacuum and then turned up if necessary.

Of course, you can see through the side of a glass fermenter, you'd have to have a sight glass in a stainless, unless it was certificated and tested to a specific level of vacuum......... implosion on a nice and expensive stainless fermenter would be just that...... expensive !

As to how much of the product aroma might be lost with the de-gassing process, I have no idea on that one.........

regards

fatbloke
 
Implosion is not an issue, as mentioned, the tank has a safety valve that will open and let air in if pressure goes below the value you set it to. The manufacturer has said that 0,4 atm is no problem.

The kind of answers I'm looking for is:

Do you need to go to a certain pressure (0,xx atm) in order to draw out CO2 all the way from the bottom (due to the added liquid pressure of 1,8 m liquid), or is any pressure below 1 atm fine?

What is the difference in time that various pressures would need to be applied to do the job? 0,4 atm compared to 0,6 atm, compared to 0,95 atm for example.

In terms of preserving aroma would a higher pressure, say 0,95 atm applied for a whole day, be preferable to 0,4 atm applied for 20 minutes, or vice versa (assuming both of those would do the job)?
 
You don't need to worry about gas trapped near the bottom of the tank. Your tank is not big enough to create much, if any, gradient of dissolved gas in the liquid. The liquid will act to uniformly disperse any gas that is dissolved in it, so application of a vacuum at the top surface will eventually remove most of the gas in there.

Time is difficult to predict, because it depends on a non-linear relationship between the vapor pressure of the liquid, that of the gas, and the absolute pressure at the air-liquid interface. Still, somewhat to common sense, a greater vacuum will pull more gas out of solution, more quickly.

As to what the ideal gas extraction rate would be, to minimize the extraction of aromatics, I honestly don't know. Although it seems that lower transfer rates (smaller amounts of vacuum) should bring out less aromatics, I can't say that with certainty. If you are going to try to vacuum de-gas, then I'd suggest doing an experiment with several smaller volumes, where different degrees of vacuum are applied to each. Then once the CO2 has been extracted to the point where it is no longer noticeable in the mead, do a taste/smell test of each one. You're going down a road that few have traveled before you!
 
Thanks for the reply Wayne. It's good to know that I won't need to worry about trapped gas. Though a small scale experiment would be a good idea, I don't believe I have what I need to perform it.

I saw in some other thread that you have a manual vaccuum-pump. Do you have any hunch as to what pressure you go down to when you use it for your own mead? And are you usually satisfied with the aromatics after use?
 
The gauge on that pump is calibrated to show relative vacuum in inches of mercury, a rather archaic method of measuring pressure differences. However, I am very gentle with the vacuum I have pulled using that device (especially since I don't want to overstress my glass carboys), so generally I will use it in the 5 to 7 inches of mercury (2.5 to 3.5 psig, or 0.17 to 0.25 atm) range of vacuum. I have not noticed a significant attenuation of aromatics from the mead when subject to that level of vacuum.
 
With a constant attention to the vacuum (to keep it in that range), approximately an hour was all that was necessary for a still mead. However, I did find that the "Wolf Moon" neolithic recipe experiment that I did several years back took a lot longer. Even though the yeast were finished fermenting (and I had racked a perfectly clear mead to a carboy that let me verify there were no lees left), something kept releasing gas in there for several weeks. I would draw a vacuum, apparently all the gas would be gone, but then a day or so later I would see activity in the airlock again. That was very strange - and I suspect that you won't see anything like that in a finished mead.

For your volume, assuming you can keep the same level of vacuum in the tank, and have roughly the same proportion of liquid exposed to the headspace in the tank, I would expect it to take a little longer... but not much.
 
What do you think it was? Some form of malolactic activity?


In the more common cases. Do you think speed and the inverse of the level of vaccuum will be somewhat proportional?

So if I was okay with it taking 5 hours for example, and 0.2 atm would have it done in 1 hour. I'd then need around 1/(((1/0.2)-1)/5)+1)=0.55 atm? and if 24 hours was okay I'd need around 1/(((1/0.2)-1)/24)+1)=0.857 atm?
 
Just to comment on vaccuum

As I have had trouble de-gassing my mead, I would also like to add a few comments here:

1. Make sure the container is stainless, or some other 'fixed' material. HDPE (thick food-grade plastic) will cave-in under vacuum (like a milk jug). I couldn't even pull 5 hg without it collapsing.

(gauge link for units here http://www.hyvac.com/tech_support/Vacuum Gauge Types.htm)

2. I think de-gassing in 'stages' is another way to ensure you are getting all the c02. So pull for 1 hour at full vacuum (30 hg on the gauge above) and then let it rest another hour or day, then pull again. I ran full vacuum on 700 gallons for 30-60 minutes over a week period, and it did make a difference, but there was still a TON of C02 in the wine after we racked to the HDPE. Then after it was in the HDPE we couldn't pull vacuum because of the plastic collapsing problem.

Aromatics will re-group after you place the wine under vacuum it just takes about 2 weeks if it has some residual sugar, and maybe 3-4 weeks if it is a dry (in my opinion).
 
IanB said:
2. I think de-gassing in 'stages' is another way to ensure you are getting all the c02. So pull for 1 hour at full vacuum (30 hg on the gauge above) and then let it rest another hour or day, then pull again. I ran full vacuum on 700 gallons for 30-60 minutes over a week period, and it did make a difference, but there was still a TON of C02 in the wine after we racked to the HDPE. Then after it was in the HDPE we couldn't pull vacuum because of the plastic collapsing problem.
Click to expand...

Dang, that sounds scary. Did you still have lees left at the point in which you were de-gassing. Had you filtered it? If so, what level of filters had it gone through? (I still have not fully decided what level of filter I want to go down to)

De-gassing will be the last thing I do, right before bottling, and I plan to keep the vaccuum going at a low level during the actual bottling, since my filler has a priming pump, that should be able to pull the mead out under a low vaccuum. There is also a possibility to argonflush the bottles before putting the mead in. Hopefully that will be enough to make sure the CO2 stays out.
 
De-gassing should probably not be the last thing done. In order for fining agents to clear the mead efficiently, it needs to be still. De-gassing should probably be done before fining (if you are fining - if you aren't fining, you may have sediment forming in your bottles later).
 
Well...now I'm in turmoil.

I bottled a single bottle a few days ago from a tank that had been standing with mead in it for about 4 months. It's clear, but a certain haze has formed in the bottom. So, I think you might be right.

I think that's enough evidence of protein instability, and that I probably do need to fine?

I guess I'll fine the meads that I have now. I cannot apply the pump to the secondary containers they are in, unfortunately, as the floating lid wouldn't be stable enough to handle it. Also I don't want to degas in my fermentation vessels for the meads coming in soon, because they don't have a safety valve, and the metal is not so thick in them.

What I could do once I have the pre-bottling tank (in a few weeks) for new meads, is run them into that for a quick de-gas, and add the fining agents, before they go into the secondaries.



The fining agents will only have around 30-40 days to act on the meads that would be bottled first, if I do it as quickly as possible. Do you think this is sufficient, given they have already been standing a long time. What would be the ideal way to add them at this stage? Just drop them in from the top, and do nothing, as to not disturnb the sediment? Or to pump the mead around a little, to stir things up, and make sure they get around?

Do you think filtering could be skipped, if fining is done instead? Because if filtering doesn't solve the issue of total clarity, it's just an unneccesary step.
 
hmmm

Here is my advice based on experience with your exact questions.

1. Filter down to .5 microns in two stages (1 micron then the .5 micron)
2. Fine your mead (read online the thousands of articles) or just use clay like I did (it worked)
3. Start de-gassing your wine now and do it in stages. One 'final' de-gas before bottling will help, but honestly I doubt you will get it all if you have only had the wine for 4 months of aging.
4. 30-40 days is fine for fining agents to finish but remember you need to pump out of that tank (leaving the fining agent behind) and then I would suggest letting that racking rest for at least 30 more days. My mistake was I bottled out of the tanks with the fining agent, and it has come out 95% clear, but that last 5% collects in the bottom of every bottle, and get's mixed in when we have the wine in our customers hands. Disappointing, and so next time we will wait another 30 days after fining and racking before bottling this time.
5. We filtered at 10 micron from primary to secondary after 6 weeks of crash cooling, and then at 1 micron at bottling time (out of the secondary). Next time we will go to the .5 micron. People like a crystal clear wine, water clear, and they like that more than the smidgen of flavor that MIGHT get lost from going down to the .5 micron mark.

also, one note on vacuum pumps. They all suck except rotary vane. Buy an Alcatel Rotary Vane used off ebay for 250 and be done with it. All the other diaphragm style pumps will fail and you can't repair them, so it is a total loss.

my .02 cents, brad or others may feel differently.
Ian
 
I'm not a commercial producer so take my "homey" approach with a grain of salt.

Step 1 - De-gas the mead. That will speed clearing. Letting it come up to room temp will drastically shorten the time it takes to de-gas.

Step 2 - Using fining. You can test for protein stability and should probably do bench trials to determine the lowest amount needed to prevent protein instability.

Step 3 - Filter with 0.5 micron nominal filter. This will remove any left-over fining agent and leave things crystal clear. After fining if it has cleared enough, you may be able to do filtration in one stage rather than two.
 
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