You know how wine people are always swirling their wine, twirling their glass to let in more air, pouring each bottle into a fancy glass decanter with a thin neck and a wide base? They do this because oxygen helps to bring out the flavor in wine. The younger the wine, the more tannic the structure, the more that a bit of air will help bring forward the fruit flavors, while softening the harsher elements. They've even invented fancy machines to help oxidize your wine more quickly by pouring it though a high-tech nozzle. When you shell out for an expensive bottle, you want it to taste right.
While aeration is good for a freshly-opened bottle of wine, too much oxygen is a bad thing. Oxidation is one of the main wine faults that sommeliers will see if you recognize as they pour you that little taste after you order a bottle at a restaurant. Too much air makes white wine taste rather nutty and acidic, while turning red into something bitter and tart. You leave a bottle of open wine out on the counter for too long and it's going to turn. Finding the sweet spot is every wine drinker's goal. However, here's something that most people don't know, even the folks who drink wine every single day: sometimes you don't want to decant your wine. Sometimes an aged bottle of wine is so fragile that aeration will only begin the process of breaking down what little structure is left in the wine. 1968 Montrose? I'm not going to decant that. I'll be praying that I can get a few glasses down before the whole thing turns to shit.
If you want to get scientific about the whole thing, here's a good definition from the Sommelier Journal:
Wine is a complex soup of chemicals, many of which are created by yeasts during the fermentation process. Any mixture of chemical entities will try to rearrange itself into the most favorable energetic state. This is the principle of entropy. In simple terms, it means that the various molecules in wine will swap tiny charged particles called electrons, depending on what is known as the redox state of the wine. In any chemical reaction between two partners, one entity gains electrons (in other words, is reduced), while the other loses them (is oxidized).
So, really, it's an exchange of electrons between your wine and the air. But that isn't really the answer you're looking for, is it?
One of the most common questions I get asked in the store is, "How long can I keep this whisky after I open it?" Like most questions, there is not one black or white answer. In fact, one of my biggest pet peeves as of late consists of people taking extremely complex explanations and simplifying them into simple yes or no, good or bad synopses. In any case, before I get distracted by a different train of thought, there is a very general answer to the "can" in that question, which is basically, "Years and years." You can enjoy an open bottle of whisky for some time with very little noticeable change in flavor. However, spirits do oxidize like wine. They will change on you. The question I would ask you, much like I ask wine drinkers, is: do you want to enjoy your whisky for that long?
Many serious whisky enthusiasts transfer their hooch into smaller containers as they continue to drink from each open bottle. The reason being that as more whisky is taken from each open container, the more that room for air is created, speeding up the oxidation process. Putting booze into 375ml bottles or 200ml minis is a way to slow the reaction. I know people who do this for wine as well. They don't want to drink the entire bottle so they immediately pour half of it into a 375ml bottle and shove the cork back in, leaving no room for air to mingle with the wine.
Now, before you freak out and start siphoning off your entire collection, I do not do this personally. I usually don't notice oxidation all that much, mostly because I don't have many old bottles lingering about. I now tend to drink what I have within a four to five month period. However, there are some bottles that have been sitting on my desk for almost a year, with only about a fifth of the bottle remaining. They definitely do taste flat, or at the very least less impressive than they once did, but they're still perfectly enjoyable. I'm revisiting this phenomenon now because of the flurry of emails I received today regarding yesterday's Four Roses post. What's going on with my bottle? I can tell you why some wines oxidize faster: it's usually because they're older and less stable. I cannot tell you why certain whiskies oxidize faster. It might have something to do with the proof, but I honestly don't know. If anyone does know please send me an email so I can post it here on the blog. What I can tell you is that my bottle of Four Roses 2012 LE Small Batch tastes more astringent than it did when I first opened it almost four months ago. It's still completely fine to drink and I just enjoyed a glass only moments ago. Nevertheless, I don't plan on nursing this one along.
I know some people in the industry who consider eight months to be the average time before oxidation starts to change the flavor of an open whisky bottle. However, I believe (although I'm not scientifically positive) that it does depend on how much empty space exists in the bottle. If the cork is tight and the surface area small, then you should be alright. However, there is no one simple answer. A website called Cellar Tracker, where wine enthusiasts go to read up on other wine drinkers' tasting notes, is a place to find out how a bottle of wine is reacting to its age. A standard review might read:
4/2012 - Opened this evening. Wine showed nicely, soft tannins, but it oxidized quickly. Do not decant.
We wine geeks read these first-hand accounts to help us with our own experiences, helping ensure maximum enjoyment. However, there are no guarantees with alcohol. As much as we try to summarize it, generalize it, simplify it, and categorize it, there are simply too many what-ifs and could-bes to do so. How did you store it? Where did you buy it from? How hot is your house? How cold is your house? It's enough to make your head spin. That's exactly why people try and create general rules of thumb to help alleviate the pressure. Despite what you hear, however, you can't simply tell someone that wine will eventually go bad while the high alcohol content of spirits gives it a permanently stable shelf life. It's not entirely true. It's not completely wrong, but there's just much more to the question.
Very few of our conceptions about booze are entirely true. Be weary of anyone who tells you otherwise.
UPDATE: SKU reminded me about his post from last year here - check this out for an actual experiment with analysis.