It's that time of week when we answer the questions you're too drunk or shy to ask...This question comes from Brian:
How long does an open bottle of vermouth keep? I recently got turned on to martinis with actual vermouth in them, and I want to make them at home, but I don't drink all that much.
Martinis SHOULD have vermouth in them, Brian. Otherwise, it's just a chilled vodka or gin, up, but that's another topic. Vermouth is a little different than normal wine in that it's fortified, meaning alcohol is added to the wine. Most vermouths run 16-18% alcohol, which is little more than some high octane American red wine. Because vermouth has been fortified and aromatized with secret herbs and spices, it will last longer than a regular bottle of red or white wine.
When you make vermouth, you essentially cook the wine and steep herbs and spices in it; then you can boost it with a little vodka or brandy. Cooking the wine is another way to oxidize it quickly, which is what happens to wine after you open it. The oxygen kills the flavor over a short period of time. When you've already oxidized the wine, you give yourself more time to drink it.
However, any time you have an aromatic beverage, those aromatics will lessen over time. For most commercial vermouths, give yourself a month to finish the bottle. I find that white vermouths, be it dry, bianco or sweet, keep a little longer than red vermouth, but it's easier to tell when red vermouth goes south. It tastes like an old open bottle of wine with potpourri in it.
I know the the tendency with nice bottles of olive oil or booze is to want to save them, make them last, but you don't get your money's worth from a two month old bottle of vermouth, period. And like rancid olive oil, it's not always super obvious the vermouth's gone south; it will just smell... less and have a far less pungent flavor.
I use whatever vermouth I can find in a half bottle because I don't drink that many martinis at home, but I do like using vermouth when I'm cooking. I buy two bottles of my favorite vermouth, opening up a fresh one when I taste a bottle starting to go south, then relegating that bottle to the kitchen. I'll buy nicer vermouth for sipping (it's great on the rock in the summer) and make sure to run through it when I have guests over. Know that the finer the vermouth, the more nuanced and delicate the flavors, the quicker that smell and taste will dissipate and, saving it or no, you won't be getting your money's worth.
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