I made a dish that used a small amount of wine and now I'm wondering how long I can keep the rest of it for next time. I know you wouldn't want to keep good drinking wine around long after opening it, but does the wine get too bad to use in cooking quickly? It's Chardonnay, if it matters. Thanks!
Opened wine spoils fast. Red wine lasts about 1 day, white wine lasts about 3 days. You can prolong this slightly by putting it in the refrigerator, but only by a few days at most, and it depends on the wine.
It may be "safe" to consume for much longer, but the taste will be way off, even for cooking purposes. If you've opened it - finish it. ASAP.
There are exceptions: "Cooking wines" such as cooking sherry and rice cooking wine have an array of preservatives added and will keep for much longer. But don't leave perfectly good Chardonnay just sitting around to oxidize.
The trick is that you won't want it to oxidize (although, red wine needs to 'breathe' to reduce some of the tannins, which is why @DanielBingham said it might improve.) So, if you just need to hold it for a few days, store the bottle upright (minimize surface area exposed to air), and not on the door of the fridge -- it'll get jostled and mix air into it.
They also sell gadgets that inject nitrogen or other non-oxygen gas into bottles, or things to suck out the air, etc. But if you're not much of a wine drinker, from your earlier comments, I wouldn't bother. (hell, I don't even know if they work).
Oh -- boxed wine will last longer -- because there's a bag inside the box, when you pour out wine, the bag deflates, so air doesn't go back in (or not much of it). You can hold boxed wine for a week or two, maybe even longer without problem.
If you're not much of a wine drinker, and only cook with the wine -- you might want to consider freezing it -- as with everything else -- an ice cube tray, freeze, transfer to zip-top bag. Then, when you need little for a sauce, you can just thaw out of a cube or two. It might not be as great as "fresh" bottle of wine, but if you're cooking with it, most people won't notice the difference, and it'd still be better than a dedicated "cooking" wine.
I'm surprised this simple cliche answer isn't here yet, so here we go:
"If you wouldn't drink it, don't cook with it."
This can apply both to which wine to buy and to if that week old bottle is still ok to use.
For white wine, I always use dry Vermouth. It lasts forever unrefrigerated, doesn't cost much, doesn't sour, and it's a damn fine substitution if I do say so myself. The only time I use anything else is when I plan on using the better part of a bottle, in which case the specific character of the wine is more important.
Keeping an actual nice white wine? It's not going to happen. Even in a refrigerator it'll be going off within a week of being opened. And crappy "cooking wine" brand wine doesn't even bear consideration.
Red wines are even worse, because they oxidize rapidly on contact with air, and tend not to be refrigerated at all. I use Sherry in the place of red wine in some dishes, but I tend to use red wine most in stews and braises and there I tend to measure by the bottle.
For cooking wine, it can keep for weeks in the refrigerator, depending upon how picky you are about the flavor. White Wines especially, we've kept for weeks or longer and the flavor was not changed significantly. Admittedly they were cheap white wines, but that's what we usually used for cooking. Red Wines, I don't know about, but I would guess that if you kept them in the fridge it would be about the same.
Edit: The assumption behind this is that your an average Joe cooking for yourself or your family. And keep means it hasn't turned to sour vinegar. It may not taste the same as when you'd just opened it, and you probably shouldn't do it if you're in cooking school or a nice restaurant. But if you're the average person who doesn't have a ton of income to spend on a new bottle of wine every time you want to cook with it and your question is "How long can I get away with keeping it?" then the answer is several weeks in the refrigerator.
Opened wine will spoil quickly. Reds will usually stay drinkable longer than whites, but it depends on the specific wine. The effect is somewhat similar to massively accelerated cellar aging, at a rate of several years per day.
If you have small containers with good seals that you can fill all the way to the top (I use 250 ml screw-top San Pellegrino bottles), you can portion out a newly-opened bottle of wine, and it will keep for a little while. The key is to leave as little air space as possible.
If you are making a dish that calls for a small quantity of white wine, try using white vermouth, which will keep for months in the fridge. This is what I do for risotto, which usually calls for 1/2 cup or so of wine, and the results are very good.
I have used red wine for cooking tomato based sauces, beef stews and chili for years, and at times have left the wine in the refrigerator for a few months and used it again. Of course I taste it to make sure it hasn't turned, if it still tastes good I use it (I know what good wine tastes like). I store it on it's side in a cold (34.5 degree) refrigerator. I usually spend between $6.99 to $8.99 a bottle on sale, and buy only Oregon or Washington wines. I don't know about white wines, I cook with them but also drink the same wine with the meal, typically a fish or chicken dinner.
Please don't bother EVER buying "cooking wine". This is simply nasty cheap wine that has a bunch of preservatives added.
I'm not one for reviving old threads. But, I have to throw my 2 cents in after I looked this subject up. While I wasn't born in a vineyard, my dad was 100% Italian, and most wines can be kept for several weeks in the refrigerator. And, yes. There will be a slight loss in taste. But, for most people, they can't tell.
Yet, a opened gallon bottle of E&J Pisano wine has lasted me for nearly a year sitting on the counter top with little loss in taste.
Also, as was said in another post, "if you can't drink it, don't cook with it". And, while Rice Wine Vinegar is an exception, "don't ever buy cooking wine".