Oxygen uptake with vacuum racking

[NorCal]

I hooked a small pressure gauge to my Ai1, so given the Mrs. is running a bit behind schedule, I’ll go see how much vacuum is required before transfer begins and if it changes during transfer.

 

[NorCal]

Here is the set up

Here is what the pump registers when the end is taped

This is when the water starts to transfer

This is at the end of transfer

 

[NorCal]

Those numbers are low, maybe that's a good thing. I'm assuming these wines were not previously degassed. It looks like you're getting about .3 to .4ppm pick up. More data is needed to get a handle on how it may vary, but it's a start; @mainshipfred your effort is greatly appreciated.

Some data from a 2014 OSU study indicates the following:

View attachment 53163

I had some H2S back in 2014 in a barrel of Zin. The fruit was really not so good. I had the free SO2 right at 50 and measured it after a big splash rack and using my Vinmetrica it lost about 1/2 the SO2. Not sure how this lineup with the numbers above, but it is what I use for a rule of thumb when splash racking in my little winery.

 

[sour_grapes]

Great test, @NorCal !

 

[stickman]

Just speculation, one possible reason for the lower DO on the barrel is because the wine is Petite Sirah. In general, Petite Sirah is known to have a very high oxygen appetite, often higher than Cabernet.

 

[Stressbaby]

I appreciate everyone's contributions on this thread today. My SO2 management is going to be a lot better. Also, I need to get some new equipment.

 

[Ajmassa]

Hey @NorCal was that so2 test showing 1/2 the initial ppm done immediately after the racking or did you wait a while? I ask because I’ve had the opposite experience- getting minimal results in the past. (Testing w/ titrets)
Eventually I read that binding up the free so2 this way could a take a couple months to see tests reflect it. But not sure if that’s fact or theory.
And likely infinite variables that could effect how much becomes bound and how long it takes.

 

[CDrew]

Here is the set up

Here is what the pump registers when the end is taped

This is when the water starts to transfer

This is at the end of transfer

Great data. That looks like 1/2" transfer tubing? So smaller transfer tubing would mean higher vacuum.

Looks like the move to make is to transfer to the bottom of the receiving vessel to minimize oxygen uptake.

I guess there is a balance here somewhere, because one of the advantages of vacuum racking is that it decreases the CO2 in the wine. More vacuum, more CO2 release. And splash vacuum racking, is even more effective at removing CO2, but also facilitates O2 uptake.

Interesting discussion, especially with it's implications for bottling.

 

[Ajmassa]

I can’t help thinking about all the aspects for potential human error/skewed results — co2, temp, ph test (calibrated meter, good buffers etc), so2 testing accuracy, projected DO, racking technique, weighing out kmeta, kmeta age/potency etc etc. It’s gotta be tough to be confident on something so specific w/o a proper lab.
I just round all my numbers in favor of more so2 since charts are minimums, and some vary, even so2 calculators vary. Figuring out exact binding from racking sounds almost impossible!
And considering the calculated kmeta I typically need, the 1/4tsp per 6gal rule seems to account for any potential so2 binding from DO.
However on a related topic, I have noticed higher ph wines eating up so2 at a much higher rate.

 

[mainshipfred]

The original topic was O2 uptake with vaccuum racking which rightfully so took other factors into consideration. A commercial winemaker advised me not to do vaccuum racking in the initial stages of the wine do to the fact he believes O2 is beneficial at this stage, but that's probably another discussion.

For the basis of this experiement I took a Cab Franc at 57* that was pressed on 10-27-2018, racked on 10-30-2018 and started MLF on 11-21-2018. It has been sitting in a 6, 3 and 3/4 gallon carboy since. Without taking an initial DO reading of each all three were poured into a 10 gallon water cooler (not racked just poured so O2 was introduced). The initial DO reading was 5.67%. The wine was racked back into 3-3 gallon carboys by : pouring from the spout, 2: AIO pump 3: mini jet filter pump in that order and all filled using the AIO splash racking cane. The end reading was 11.20%, 6.89% and 14.23% respectively.

@Ajmassa5983 could be correct in SO2 taking time to integrate because the original free SO2 was 7 ppm and through Fermcalc I added enough Kmeta to bring it to 50 ppm by mixing it with wine before adding to the bulk. However the first follow up reading after 30 minutes or so was 13 ppm and after waiting another 30 or so it jumped to 28 ppm. For this reason I didn't take SO2 reading after it was racked.

I realize it's only one test but I feel it may hint toward vaccuum racking has less uptake than other methods.

 

[Ajmassa]

Tons of data going on here!
Those results sound about what would be expected I think. So to bring it back to stressbaby’s original thought now would need another comparison test of:
Gravity siphon bottom fill
Gravity siphon splash rack
AIO bottom fill
AIO splash rack
Before & after DO levels
Test done 3x on 3 different wines to confirm result trend.
I expect a full report on my desk by Friday!
(Fred let’s set up a GoFundMe for refills on those DO reagents lol)

 

[Johnd]

And when all of that data is logged, you’ll have to figure out what it means. Is a wine better or worse for limiting oxygen exposure? When is it beneficial and when is it harmful, and in what quantities at any particular stage is it a plus or minus? Does vacuum racking prematurely expose your wine to oxygen? When it’s saturated with CO2, it can’t be saturated with O2, so should we allow the transition naturally? My questions are endless.

I’m an O2 and big red wine lover, and treat my big red wines to a dose of O2 whenever the opportunity arises during normal operations. Saturated with CO2 til shortly after MLF, exposure is probably immaterial before then. I keep all vessels properly topped and sulfited, but splash rack at every transfer, racking off of sediment, into barrels, out of barrels, before bottling, etc.. Never had an oxidation issue, nor a reductive wine, and my sulfite protocol hasn’t resulted in a failed / diseased bottle yet, but it doesn’t make the investigation and experimenting any less interesting........

 

[sour_grapes]

When it’s saturated with CO2, it can’t be saturated with O2

Not at all sure that is true. Maybe one of the chemists can weigh in?

 

[Johnd]

Not at all sure that is true. Maybe one of the chemists can weigh in?

Hmmmm, guess I’m not sure either, just seems to be something that’s planted in my head, though I can’t say where it came from. Yet another mystery.....