The Scam of Wine Vacuum Pumps
If you're even just an occasional wine drinker, you might have noticed a type of product being sold in just about every shop that sells wine accessories: the handheld wine vacuum pump. A number of different manufacturers make it (VacuVin's Wine Saver being the most common), and though they each have a slightly different design, they're all essentially the same. The purpose of a vacuum wine pump, when used in conjunction with one of the specially-designed rubber stoppers included in the kit, is to "remove the air from opened bottles of wine and prevent the oxidizing effect of air from spoiling the unfinished wine." This ostensibly allows you to open a bottle of wine, drink a portion of it, and then preserve the rest in a 'vacuum,' thereby allowing you to finish it at some later time. Well guess what? It's a bunch of B.S.
First of all, there is simply no way to create a perfect vacuum by manually pumping the air out of a vessel. Ask any physics teacher and s/he's bound to agree that the air pressure around us is entirely too high for some removable rubber stopper to keep any significant amount of air from seeping into a bottle. To create a perfect vacuum anywhere near sea level — and a perfect one is precisely what you'd need, in order to make a difference — the sort of equipment required would be a hell of a lot more sophisticated than a $15 plastic hand pump.
Secondly, it really doesn't take that much oxygen to spoil the remaining wine in an open bottle. This is something that occurs on a molecular level, so even if you were an obsessive and masterful vacuum pumper, the tiny stream of air gradually seeping past the imperfect rubber seal would be enough to oxidize your wine almost as quickly as if the bottle had been left open.
Now, don't get me wrong; there is such a practice as preserving wine by protecting it from the breakdown of oxygen. In fact, wineries actually need to do this quite often on a large scale, several times during the production process. But what wine producers use to keep oxygen away from wine is not a vacuum per se, but a blanket. There are a few gases that work very well in displacing oxygen in a container of wine, by creating an invisible blanket or barrier between the wine below and the air above. Nitrogen, carbon dioxide, and argon are often used to this end, either individually or in some combination.
Interestingly, there are a couple of consumer products (Private Preserve being the most common) that offer gas in an aerosol can that you spray into open wine bottle. And I have to say this method actually works… to an extent. In fact, I used to use this product. But the reality is, I almost never keep an unfinished bottle of wine around for more than two days; and as I've mentioned before, wine is quite frequently better the day after it's been opened.
So my advice is this: don't bother with gimmicks meant to preserve wine. None of them will completely halt the oxidation of wine once it's started and, frankly, they're just a waste of money.