I agree that partial vacuums are a possible complicating matter wrt diffusion. I think this is an excellent question for Alan/Al! I'm assuming the 'normal' diffusion laws/rules apply here, and the diffusion is accelerated due to the small population of <insert here> molecules. But I'm just guessing/assuming here.John Morris wrote:That's very interesting. I suppose what you're saying about rapid diffusion into a gas explains the burst of aromas when you first pop the cork.Eric Lundblad wrote:If you pour out half the bottle and insert a repour, it'll absorb all the oxygen...21% of the air, so it'll have a partial vacuum (21%).John Morris wrote:
Even without a pump, you've vastly increased the headspace so you can still lose aromas.
Aromatics occur because of diffusion (within wine, and from the wine to air). Diffusion in a gas is extremely fast...repour depends on this to absorb the O2 quickly. But diffusion in a liquid is very very slow...years/decades slow. So you'd lose aromatics from the very top layer of the wine. And it's not a continious loss...it'll reach a steady state fairly quickly (same amt of aromatic molecules going into the air as are going back to the liquid). This fact, aromatics only comes from the surface, is why we like large wine glasses, and like to swirl them.
So loss of aromatics isn't an issue imo. I've tested this many times over 1+ year periods via my wine in partly filled kegs (used for topping barrels, head space in keg is nitrogen)...no loss of aromatics.
What about changes in pressure? When you cork, does that put the air in the headspace under slight pressure? I've been curious about that.
Do you agree that the vacuums are a different story? I used to use the Vacuvin. I found they were OK if the bottle was, say, 3/4 full, but below that, and after multiple pumps, the wine lost all aroma; they were flatter than I would find just recorking the partially full bottle. (I always refrigerate opened bottles.)
The reason I challenged the idea of the Repour is that virtually all the discussions here about devices like this or Coravin, or about decanting, start from the assumpion that the only factor at play when you expose to wine to air is its interaction with oxygen. Some of Jamie Wolff's articles talk about factors affecting diffusion of aromatics, including alcohol and sugar levels. That made me aware that there's more going on than just oxygen.
Alan R's data in an earlier thread about how little oxygen diffuses into a liquid also suggested (to me, anyway) that something else is also going on in a decanter.
Jamie Wolff? Did you mean Jamie Goode? I've been spotty about keeping up lately, so I missed all/some of the discussions about aromatics and diffusion. I can certainly see that alcohol & sugar would change things, but mostly in the area of liquid to air transition. I wouldn't thing the diffusion in the liquid (wine) would change enough to have any material affect. Assuming that's true, my thoughts on the 'depletion' of aromatics being limited to the surface still seems reasonable (to me).