I was cleaning out my liquor cabinet the other day when I came across an unopened bottle of sweet vermouth tucked way in the back. Upon inspection, I realized it had been sitting there for at least a couple of years past its “best by” date. My first thought was, can old vermouth that’s been sitting around for so long actually make me sick if I try to use it in a cocktail?

This seemed like an important question for any home bartender to understand, so I decided to dig into the science behind vermouth’s shelf life. Here’s what I discovered about whether consuming old, oxidized vermouth can potentially cause illness.

Why Can Aged Vermouth Cause Sickness?

First, let’s start with what vermouth actually is. Vermouth begins its life as a wine, often a neutral and aromatic white wine. However, the wine is then fortified, meaning a spirit with a high alcohol content such as brandy is added. The resulting vermouth typically contains between 16% to 18% alcohol by volume.

Like any wine or spirit, vermouth can oxidize as it sits in an opened bottle over a long period of time. The alcohol content slowly evaporates, leaving behind a higher concentration of the wine’s sugars and bitter compounds. Bacteria and yeasts present in the vermouth act on these sugars, causing fermentation.

When you consume aged, oxidized vermouth, these newly fermented sugars can interact badly with your digestive system. They may upset your stomach, cause bloating and gas, or even trigger vomiting or diarrhea. So in this sense, yes – drinking vermouth that’s old and overly oxidized can make you sick.

How Long Does Vermouth Last Before Spoiling?

Knowing that vermouth has the potential to make you ill if left for too long, how long can you actually store an opened bottle before it goes bad? Some sources claim vermouth lasts indefinitely, while others say it has a relatively short shelf life of just a few months.

The truth lies somewhere in the middle. An unopened bottle of vermouth, stored properly in a cool, dark place, can maintain its freshness and flavor for many years. Once opened, oxidation begins taking place. However, the alcohol content helps inhibit microbial growth. With a tight seal and refrigeration after opening, vermouth should retain good flavor and aroma for at least one year.

Beyond the one year mark, vermouth’s taste and bouquet will gradually fade. While it may not make you sick immediately after a year, its quality deteriorates to the point where using it in cocktails or cooking is not recommended. Consume vermouth within 3 years of purchase to be safe.

Dangers of Consuming Aged Vermouth

Why take the risk of drinking vermouth that’s been open for longer than a year or has clearly oxidized? There are a few potential dangers:

• Oxidized vermouth often tastes sour or vinegary as acetic acid bacteria grow. This leads to unbalanced, unpalatable cocktails.
• Mold growth, oxidation, and chemical changes in the vermouth can introduce unhealthy compounds.
• The sugary, fermented vermouth may upset your stomach or cause other gastric distress.
• In rare cases, dangerous foodborne pathogens could grow in the vermouth.

While the alcohol content in vermouth inhibits microbial growth to some extent, it does not fully prevent spoilage after prolonged aging. Consuming very old vermouth is not worth the risks.

How To Tell If Your Vermouth Has Gone Bad

Vermouth’s aroma and flavor provide the best indicators of whether it has oxidized or spoiled. Here’s what to look out for:

• Lack of aroma – Fresh vermouth has a strong, pleasant herbal and botanical smell. If you can’t detect much aroma, it has likely oxidized.
• Vinegar smell – A vinegar-like smell means acetic acid bacteria have grown. This vermouth is over the hill.
• Color changes – Look for fading of the original color or a darkening hue. This is a sign of chemical breakdown.
• Loss of flavor – Your vermouth should taste bright and herbaceous. Dull, flat, or sour flavors indicate oxidation.

Trust your senses – if your vermouth doesn’t seem right, play it safe and replace it with a fresh bottle.

What To Do With Bad Vermouth

If you determine your opened vermouth is past its prime, don’t just pour it down the drain. Here are some thrifty ways to salvage and repurpose the oxidized vermouth:

• Simmer it into a flavorful sauce for meats or vegetables.
• Reduce it down to a syrup and use in cocktails in small amounts.
• Infuse vinegars or oils with the vermouth for bold homemade condiments.
• Use as a base for poaching fruits like pears or quince.

In cases of severely spoiled vermouth, it may be safest to dispose of it entirely. But with a little creativity, you can often find uses for vermouth that’s merely oxidized and lost its nuance.

Proper Storage for Opened Vermouth

To get the most longevity out of your vermouth once opened, be sure to store it properly. Here are some tips:

• Keep opened vermouth refrigerated at all times for shelf life up to 1 year.
• Store in a cool, dark cabinet if refrigeration isn’t an option.
• Seal the bottle tightly with its cap to limit oxygen exposure.
• Use an argon or nitrogen preservation spray if you want maximum freshness.
• Consume within 2-3 months for best flavor if not refrigerated.

Avoid leaving open vermouth sitting on your bar cart or countertop, as heat and light hasten oxidation. With proper storage, you can feel confident enjoying your vermouth for months after opening.

Additional Signs Your Vermouth Has Spoiled

Aside from losing its enticing aroma and flavor, here are a few other signs that opened vermouth has crossed over from oxidized to spoiled:

• Foam, bubbles, or effervescence when you pour it
• Cloudiness or particles floating around
• Slime, film, or mold growing in the bottle
• Separation between alcohol and other ingredients

If you observe any of these issues in an opened bottle of vermouth, it’s best to discard it entirely rather than trying to salvage it. The oxidation and microbial processes have simply gone too far.

The Verdict on Old Vermouth

So back to my original question – will consuming old vermouth that’s been stashed away for a few years make me sick? Based on my research, the answer is yes, it certainly could if the vermouth is far beyond its prime and has become overly oxidized or fermented.

The takeaway is that vermouth isn’t meant to age forever like a fine wine or spirit. Once opened, it should be enjoyed within a year or two at most. Properly stored vermouth won’t necessarily make you ill once it loses its flavor subtleties. However, severely aged vermouth poses real risks of stomach issues or even dangerous bacterial contamination.

Always inspect and smell your vermouth before using it. If anything seems off, trust your senses and replace it with a fresh bottle. While it may feel wasteful to discard oxidized vermouth, it’s the safest option to avoid getting sick from a bad batch. Your craft cocktails and health will thank you!