Another nice note, Jeremy…
I’m convinced that long slow elevage is a key ingredient to getting such intensely crystalline whites…long ageing sur lie, naturally protected from oxygen as long as there is outbound gas.
I asked Seb when tasting with him if he has ever met Mounir Saouma, whose slow and low elevage with uncanny intensity of whites came to mind. He said nope.
I don’t think positive gas pressure prevents oxygen ingress.
Yep, intuitively we think this, but I don’t think I’ve ever seen evidence to prove it…
Positive pressure implies that you release gas when you open the bottle - like Champagne, in extremis. But after 3-4 years it’s a very rare wine that retains a little prickle of gas in its texture, so think it’s equally probable that the CO2 has fled the scene. Alternatively thinking, if bottled with positive pressure, the gas eventually ‘forces’ it’s way out - so couldn’t that be a route back in for other things - a route that might otherwise have not been there? Just thinking out loud and certainly without evidence…
I’m talking in elevage, not in bottle.
Interesting if my simple logic is off base, but I thought that that was sort of a common sense real thing…
Any winemakers want to chime in?
Ha! Of course, buyers are much more interested in protection from oxygen once the bottles are in their cellar 
CO2 while in elevage could help avoid some oxygen exposure, sure. Primarily (I would think) when there’s headspace due to evaporation.
I wonder if consumers positively associate suspended CO2 with minimal intervention- fewer rackings, slower ML, less SO2, etc.
This wasn’t what Robert was getting at at all, but it is an interesting tangent: adjusting CO2 levels at bottling very precisely is very fashionable right now among enologists in Burgundy (and I would guess elsewhere) and I know that a number of them really encourage their clients to do this for both red and white wines. There is quite sophisticated equipment for it available: e.g. http://michaelpaetzold.com/fr/produits/carbonication-décarbonication So this is not just about retaining gas from fermentation but to do with adding it. The idea is to bring “freshness” to the wine without adding so much that tannin / structure are emphasized. Given that my main interest is in wines made to age 20+ years, it has typically struck me as a bit unnecessary; and despite the enologists’ best efforts I find quite a few of these gassed red wines taste unnecessarily firm on release from the CO2 addition (of course, it doesn’t help when the same enologists are also recommending producers use extraction enzymes during the fermentation).
The answer is yes. As I understand it, this functions in a number of ways. Oxygen will only dissolve into the wine in proportion to the pressure of gases, so the more CO2, the less O2 (so if CO2 is actively being evolved by ongoing alcoholic or malolactic fermentation, oxygen is effectively excluded). CO2 being a heavy gas will also help prevent oxygen ingress (though supposedly most oxygen ingress actually comes via topping up). And dissolved CO2 also changes the wine’s pH and thus its redox chemistry.