How to keep sherry and other wines for cooking once opened?
I have a bottle of sherry just opened for a recipe. It's a California sherry, not hugely expensive, but I'd like to keep some on hand for future cooking if possible.
What's the best way to keep it longer term for this kind of thing? Freeze in ice cube tray and store in plastic vac-pac baggies in the freezer? Or is there something I can add to them to give them shelf life in the cabinet? (I have ascorbic acid powder from the science supply, and citric acid powder also, in case these are options. I would expect they'd change the flavor profile but please let me know if they'd be of use.)
You'd need a very cold freezer to freeze sherry. It's a fortified wine - extra alcohol is added to it when it's being made, so it wouldn't freeze too well. And you're right that you don't want to add things to your wine, that would ruin it.
The way to keep sherries or other cooking wines is the same as any wine. The main enemy is oxygen, which will interact with the wine to "oxidize" it. Sherry's partially oxidized during the making/aging of it, but still, oxygen is the enemy. And of course, as with any chemical reaction, the lower the temperature, the slower the reaction.
So if you have used up half a bottle of sherry, transfer it to a 375ml bottle. Or you could add some (sterilized) marbles to the bottle. Another method is to combine more than one bottle into a single bottle. The idea is to leave as little air in the bottle as possible.
Restaurants and wine bars accomplish the same thing by replacing the air in the bottle with nitrogen, so there's no oxygen left in there, and no chemical reaction. There are also gadgets like the Vacu-vin, which pumps a certain amount of the air out of the bottle. But it still leaves a lot in the bottle, so it doesn't work that well.
So if you get the maximum air out of the bottle, and then put it in the fridge, you should get maximum mileage out of your wine.
Vacu-Vin pump or else nitrogen gas and shove the cork back in... and then fridge. If your purpose is cooking only, it will be good for months.
Others have made this suggestion before on similar posts: It may be worth purchasing those four-packs of small wine bottles (usually for picnics), "use" the wine in the bottles, and then use these bottles for storing your remaining wine in the fridge.
As others have mentioned, oxygen is wine's enemy where storage is concerned. We've used both the nitrogen and the Vacu-Vin, and they do make a difference, but even still, we have noticed some change a few days later.
Everyone is giving really good suggestions about preserving wine. But I have to ask...what are you using this for? If you're just deglazing pans and the like, you are not going to taste any small changes in a slightly oxidized wine. FWIW, I'd just stick the cork back in the bottle and put it in the fridge. Then, if you're going to do something where you'll be featuring the wine (a beurre blanc, or a wine based poaching liquid for fruit) you can always open another bottle, especially considering that these applications would often use a whole bottle on their own anyhow.