To address this, there are many solutions available: google for wine preservation system.
The various solutions fall into one of these categories:
- Replace the bottle with a bag that can be squeezed so the wine comes up to the top, leaving no air to react.
- Displace the wine up to the top of the bottle by pouring clean inert beads into the bottle.
- Pour the wine into a smaller bottle, and have a set of bottles of various sizes.
- Remove the air from the bottle (by creating a partial vacuum in the bottle).
- Replace the air in the bottle with an inert gas.
- Bags work but turn an aesthetically pleasing bottle of wine into an ugly plastic sack. And the sack is difficult to clean and dry. Plus I don't really like the idea of wine sitting in contact with plastic for days.
- Beads work but are hard to clean and then dry (a colander is good for cleaning, but drying is a pain, because water sticks in the voids between the beads).
- Smaller bottles don't work as well as beads, because the step sizes between bottles are larger than the volume of one bead. And the bottles are hard to clean and dry.
- Creating a partial vacuum can diminish/change the flavor of the wine, probably because it draws off useful volatiles (for example, dissolved CO2).
- Using an inert gas works very well. The step size is the size of a molecule, and when the bottle is opened the gas disperses and there is nothing to clean or dry.
You can buy an inert-gas system. They cost a lot of money, and typically even if the base unit isn't outright expensive, the replacement gas canisters are expensive (including, oddly, Hazmat fees for shipping the bottles, even though the gas is harmless). They wouldn't need to be expensive, but, like giving away the handle and charging for the blades, that's how the inert-gas-wine-preservation-system vendors make their money.
You can instead create an inexpensive inert-gas solution entirely from off-the-shelf parts. You don't need to buy anything fancy.
- Call your local industrial-gas supply shop. For example, Airgas. They are pretty much everywhere, because welders, food systems, labs, etc. need various gases.
- Ask for their smallest tank of argon. I asked for food-grade argon, and they didn't have it in the smallest bottle size. But when I asked what the "contaminants" are in regular argon, they said it was just air, and the percentage is very low. They also said that's what wineries use (they don't need food-grade). Don't worry about it.
- While at the gas supplier, also get a regulator. Show them the photo below so they know what kind of regulator you need. Ask them to install and test it. Ask them to show you how to use it (hint: you need to turn the big valve on top of the tank first, then the little valve on the top left of the assembly in the photo).
- Pay for the regulator, the tank rental, and the argon.
- Take the tank/regulator assembly and an empty wine bottle to a local hardware store with a good selection of small pipes and adapters, and ask them to make something that looks like the photo.
When filling a bottle with argon, open the small valve the least possible amount, to inject argon into the bottle as gently as possible.
When you feel you've replaced the air with argon as much as possible, quickly remove the nozzle, shut off the small valve (firmly, but don't overtighten), put the cork (or some other stopper) in the bottle, and then shut off the big value (again firmly, but don't overtighten).
Even the smallest bottle of argon lasts for ages--not much gas is used per wine bottle. We're still on our initial purchase of argon.
When you finally run out of argon, take the bottle/regulator assembly back to the supplier, and get a replacement bottle. (They just swap bottles, don't refill the one you have). Ask them to install and test the regulator on the new bottle.
Note: It's a good idea to attach a chain, wire, rope, strap, etc. to a wall and around some part of the argon tank (so it doesn't tip over and snap off the top, which is a rare occurrence but quite spectacular when it happens).
Caveat: Wineries have big tanks and special piping/techniques for sparging (filling the headspace with inert gas, http://morewinemaking.com/public/pdf/inertgas.pdf). When you manually squirt some gas into a wine bottle, even taking care not to create turbulence, you can't achieve the gentle laminar flow wineries achieve, so you probably aren't displacing all of the air so much as diluting the air. But that's still better than nothing, and in practice this has worked well for me.