Oliver, that’s exactly what I’m saying: there is a “conventional wisdom” that having dissolved CO2 reduces the amount of of O2 that can be dissolved. That’s not really true, though it’s a bit of a complicated question that depends on the history of how the wine was exposed to the gases. This is also a response to Brian’s post.
If you’re talking about gases being absorbed by a liquid, the amounts depend on a couple of things: what’s the saturation point for each gas (CO2 is about 30 times more soluble in water than is O2); and the composition of the gas that the liquid is exposed to. But just because a liquid is saturated with one gas (say CO2) doesn’t mean it can’t be equally saturated with another (like O2). You could have a wine saturated with CO2, then expose it to O2, and it would still absorb O2 until saturated.
What having some CO2 will do is reduce the pH a little, which can push the equilibrium between SO2 and HSO3- toward SO2, meaning you’ll have a slightly higher concentration of “free SO2” as winemakers like to think about it. But long term that should make no difference in a bottled wine, as SO2 will balance will continually adjust as it is used up. So I think winemakers make a mistake by thinking that CO2 is “protecting” the wine, and adding less SO2 than they might otherwise. If O2 gets in through the cork, that lower amount of SO2 will just be used up more quickly, and poof your wine will oxidize before its time.
I have no names, David. The articles where I read about adding CO2 at bttlg to “freshen” the wines
named no culprits.
So just regard it a hearsay with no credibility, like most of my posts.
Tom
I have no doubt there are producers who rely on CO2 either for “protection against O2” or to brighten a wine that is otherwise a touch flabby. I’ve absolutely experienced numerous wines that seemed to have nice acidity early on, then went flat after some time in the glass. That’s a pretty clear sign of excess CO2. The second may be a result of the first.
DCO2 in wines bottles within a year after fermentation tend to hover around 1200-1400 mg/L (that’s without racking - so your whites and Pinots). That’s just natural. I’ve worked for wineries of all sizes, and it’s very rare for a small winery to mess around with their DCO2. That’s primarily a big boy thing to knock it down.
Most chards and Pinots will be bottled around 600 mg/L, and Cabs around 200-400 mg/L. Your aromatic whites will be 600-800mg/L.
From what I’ve read, using CO2 is a bit more challenging that using the other gases to prevent oxidation as it is more soluble than the other two and therefore will then dissolve into the wine rather than ‘protect’ it against oxidation.
As others have noted, there is a tremendous amount of dissolved CO2 in young wines, especially those that are tank fermented. The sooner they are bottled, and the less movements they have around the winery, the greater the chance that these levels will be higher and perhaps ‘noticeable’ upon opening and consuming the wine - as long as it stays cool and you keep the screw cap or cork on it.
Many wineries can and do check their levels of dissolved CO2 using a simple instrument called a Carbodoser. Or you can send off for the same information from a lab. Some wineries try to hit a specific level - and if they are above it, they will sparge the wine to remove some. If they are below it, they will add some.
Why add it? Dissolved CO2 does raise the ‘feeling’ of acidity on the tongue by providing a ‘slight spritz’ to the wine - not so much that you might think it is a ‘sparkling’ wine but enough to pump up the apparent acidity. This works especially well with aromatic whites bottled with some RS, as these further counter-acts the sweetness in the wines.
This is completely legal here - I had no idea it was not legal in Austria or Germany.
Metallic feel on the palate is what I can nest describe high levels of DCO2. It’s also a huge pain in the add to get your fill levels right on a bottling line when you’re running over 1 g/L.
Been in a Kiwi Sauvignon Blanc phase lately and the warden has commented a few times about the “fizzy” palate. I’d describe it as a tingle. Seems fairly prevalent.
Yup, Brig…I particularly started to notice it in Kiwi SauvBlancs a number of yrs ago when I’d unscrew to screw-top and hear
this distinct “pop”. But whether it’s added at bottling or preserved from fermentation, haven’t a clue.
The articles I recall reading about adding CO2 at bttling was addressed to Kiwi SauvBlanc as I recall.
I’ve just been noting it more in Austrian wines over the last yr or so.
Tom
It is not illegal in the EU to sparge CO2 into tank before bottling unless you reach the threshold for sparkling wine (which iirc is over 1 atmosphere of pressure). Many producers in Germany do this and it was taught at my school there. Of course, just as many do not. If you use a DE filter and then sheet-filtration at bottling, including the requisite racking from each process as most do in Germany and Austria, you will lose most of the dissolved CO2 from fermentation. Overall, you are most likely to find sparged CO2 in the cheaper offerings from low-endish producers meant for early consumption.
Thanks for the info. Truly appreciated. I didn’t think they would ‘disallow’ this, and though it may mainly be used by ‘low-endish’ producers, my guess is that others may use it from time to time to ‘bump up’ the perceived acidity of their wines . . .
Certainly so. But generally in Germany (maybe slightly less so in Austria) for Riesling, acid is no problem. But yes, it does liven them up even more. The most traditional producers may opt not to add CO2 for philosophical reasons, but there is nothing beyond that to stop them. CO2 is cheap, and you can sparge 10,000L in a hot minute.
I think there are other possible explanations. Rising temperature is one. And sometimes the fruit and body in high-acid wines comes to the fore with air, changing the perceived balance to shift pretty dramatically, with the acid going to the background. I don’t know why that is, but in most cases, I don’t think it has anything to do with CO2.
Thanks, Bill…exactly the kind of info I’m looking for.
As far as Austria is concerned, specifically…perhaps they forbid sparging w/ CO2 afore bottling. I’m checking w/ a few Austrians that I know.
Yup, Russell…understand that. But don’t sometimes countries have more rigorous winemaking rules that
supersede the EU regulations? Just asking…I don’t know myself.
Since sparging w/ CO2 is an evil process and a manipulation, perhaps the higher Austrian winemaking standards
preclude that?
Tom
Thanks for the explanation on the different solubility of different gasses in liquid not necessarily interacting with each other. When we need to sparge out O2 from a wine (probably only winemaker on the board who deals with this from the commentary I see…) we use N2, as CO2 is not effective at driving the level down.
As far as CO2 being used as an anti-oxidative gas I have to disagree with it not being effective beyond a minor pH lowering. Any time you transfer a wine (tank to tank, bottling etc.) there is some level of surface disturbance and an increased opportunity for gas transfer. If you go to bottle (or rack to tank) with a higher CO2 level, you’re allowing that CO2 to foam off and effectively create a blanket of gas that reduces the level of O2 that is going to come into contact.
We see this at bottling all the time, as the wine will drop ~100ppm of CO2 from tank to bottle (its a simple test, akin to shaking a Soda bottle and checking the temperature) and we see lower O2 pickup with higher ppm bottled CO2 wines vs. lower ppm bottled CO2.
