How Long Will Vermouth Last Once It's Opened?

Vermouth is a very versatile fortified wine. In addition to being commonly used as a flavorful and aromatic infusion in cocktails, you can also use vermouth to add flavor to all kinds of foods. You can put sweet vermouth in clam chowder to sweeten the dish, braise your chicken in vermouth, or use sweet red vermouth as the liquid ingredient in an ice cream float to make an adult version of dessert. Although you can reach for the vermouth stored in your kitchen for various uses, you should do it in a certain amount of time once you've opened the bottle. After the first time you've cracked the screw cap or cork on your vermouth, use it within three months because that's how long it will last before it goes bad.

Within one month of being opened, vermouth will maintain its optimal flavor and smell, and after the next two months, it will have a passable taste and smell if stored properly. An opened bottle of vermouth stored longer than three months will begin to lose its aroma and flavor from oxidation because it's been exposed to air. This is why it's essential to use the best storage method after your vermouth bottle is opened to ensure that the fortified wine retains the fullness of its flavor and aroma.

Vermouth is essentially wine, so if you leave it on your home bar or table at room temperature after opening the bottle, it will begin to oxidize immediately and develop an unpleasant taste that will worsen the overall flavor of any cocktail or dish you mix it in. If you store your vermouth in a cupboard or pantry, it will also lose its aroma and flavor after a month. To preserve your vermouth's great taste and pleasing smell, store it in the refrigerator, which is one of the tips every home bartender should know.

The cool temperatures of your fridge can slow the oxidation process in your vermouth so that it sustains the strength of its flavor and aroma for an extended period. Fabio Raffaelli, brand ambassador for Martini & Rossi, explained to The Spruce Eats, "If stored in a refrigerator once opened, vermouth will stay fresh for about eight weeks, and then will still be good—although maybe not as fresh — for about two months after that." 

Now you know the best way to store vermouth to get the most out of it. But what happens if you drink or use old, opened vermouth in your cocktails or meals?

Since vermouth is a fortified wine, once the liquid has sufficiently made contact with air and heat, it will eventually convert into vinegar. This will result in the vermouth developing an acidic, sharp, and bitter flavor with a strong odor, which can happen over time. Using old vermouth in your cocktails will add a negative taste to your drink. "The magic of classic cocktails like the martini or negroni comes from the delicate balance of flavors and aromas, which can easily be thrown off by an old vermouth," Fabio Raffaelli told The Spruce Eats.

It's also possible that old vermouth can make you sick. After an extended period of time, the alcohol content in vermouth will vaporize, and all that will be left is sugar that bacteria and yeast can ferment. If you imbibe old vermouth, all of that fermented sugar may give you a stomachache or lead to bloating and diarrhea. If you've got an old bottle of vermouth at home but want to make a cocktail, discard that bottle and try the vermouth swap to amplify your next martini.