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How does a beer get skunked?

Author

Christopher Snyder

Updated on March 16, 2026

How does a beer get skunked?

Skunked beer is caused by a specific chemical reaction triggered by exposure to light, as explained in the latest Reactions video by the American Chemical Society. Brewers know this — there's a reason why craft beer comes in brown bottles or cans, as opposed to green or — shudder — clear glass.

Herein, how do you tell if a beer is skunked?

Typically beer will result in the "skunked beer" flavor when it is light-struck. And the most common types of beers to become light-struck are those in green or clear bottles like Heiniken or Corona.

One may also ask, does skunked beer lose alcohol? In a word, no. The alcohol content of beer (and wine, for that matter) is determined during the fermentation process and will not change over time. During fermentation, yeast converts sugar (or any carbohydrate source) into carbon dioxide and ethanol alcohol.

Similarly one may ask, how do you fix skunked beer?

Unfortunately, no. Skunked beer is caused by a specific chemical reaction that is due to the beer's exposure to light. (It's not a result of taking it in and out of the fridge, as some believe.)

Can bad beer kill you?

Drinking beer past the expiration date is not ideal, but in the event that you drink a “rotten beer”, just know that drinking a bad beer probably won't make you sick and it won't kill you. At the most, you can expect a bit of a stomach ache and a slight feeling of disappointment and disgust.

Can skunked beer make you sick?

Although "skunking" is considered a flaw in a beer's flavor profile, skunked beer has no ill effect, whatsoever, on the consumer of the beverage.

Can you get drunk on flat beer?

Assuming the beer is done fermenting: If you naturally carbonate, there will be VERY slightly less alcohol than carbed beer but not enough for you to ever notice a difference. In other words, it'll get you plenty drunk. Carbonation has no bearing on how drunk you get; only alcohol content matters.

How long after bottling is beer good?

two weeks

Is it safe to drink 10 year old beer?

The simple answer is yes, the beer is still good insofar as it is safe to drink. Since most beer is either pasteurized or filtered to eliminate bacteria, it's extremely resistant to spoiling.

Does beer expire?

The short answer is that yes, beer expires. But saying the beer expires is a bit misleading, it doesn't actually become unsafe to drink, it just starts to taste unappealing or flat.

Can you return bad beer?

Fear not if your beer has a funk. Though policies vary from store to store, there's a good chance you can get a replacement or your money back. And returns aren't limited to whether the beer is bad.

What does a skunked beer taste like?

Randy Mosher, in his seminal guide Tasting Beer, describes the perception of methyl or isopentyl mercaptan (skunking) as skunky or rubbery; the Cicerone program describes it as “musty, can be similar to burned rubber or cat musk.” I personally think it's a combination of skunk smell and musty basement; a skunked beer

Do beers really get skunked?

The beer is bad. Skunked beer is caused by a specific chemical reaction triggered by exposure to light, as explained in the latest Reactions video by the American Chemical Society. Brewers know this — there's a reason why craft beer comes in brown bottles or cans, as opposed to green or — shudder — clear glass.

How long before beer gets skunked?

30 seconds

Can you cook with skunked beer?

Don't cook with skunked beer – when light interacts with hop compounds in beer, sulfur compounds are produced, including 3-methyl-2-butene-1-thiol, or MBT. True, cooking with skunked beer will volatilize some of the compounds and get rid of them, but who wants a kitchen that smells like skunk when you're cooking?

What can you do with bad beer?

Here is what other brewers do.
  • Cooking with beer. The most common answer I got was to use the beer for cooking.
  • Beer Fertilizer. Several brewers suggested bad beer could be used as lawn fertilizer.
  • Making Malt Vinegar.
  • Moonshine.
  • Add more hops.
  • Snail Bait.
  • Beer Possum.
  • Just drink the beer.

Why are beer bottles Green?

Beer was stored in clear glass and when left in the sun for too long, it started to smell "skunky" – like a skunk, literally. This was because the clear glass allowed UV rays to penetrate the beer and alter the flavour. After World War II, green bottles also became popular due to a shortage of brown glass.

At what temperature does beer skunk?

When I came across a customer asking about purchasing warm beer, I attempted to dispel the myth. It's not temperature that effects the beer, but light leak - we'll get into this in a second. Beer is fermented at a cooler temperature - around 65° F for ales and 55° F for lagers.

Why is my beer bitter?

Excess bitterness is created by overuse of boiling/bitterness hops, long boil times, the use of black or roasted malts, and the use of alkaline water or water with excess sulfates.

What is Lightstruck beer?

An off flavor characterized by a sulfuric, skunky aroma, typically due to a reaction between hops' alpha acids and sulfur compounds in the presence of sunlight or electric light, indicating the presence of 3-methyl-2-butene-thiol. Clear, green and blue bottles are most at risk for lightstruck flavors.

Why does my beer taste bitter?

Meanwhile, beer's bitterness largely comes from hops. The alpha and beta acids found in hops, as well as the low concentrations of ethanol in beer, bind to three of these 25 bitter receptors, signaling a strong bitter taste to the brain when you take a sip of lager, Lovelace said.

Can you get food poisoning from beer?

It is not caused by harmful bacteria within the alcohol itself. Although there is evidence to suggest that consuming alcohol with a meal can reduce the drinker's chance of suffering from food poisoning, consuming alcohol after symptoms have appeared will not make them go away.

Can you drink 3 year old beer?

Many beers taste perfectly fine after their expiration date has passed. Some beer drinkers even prefer the taste of certain types of beer after it is technically out of date. Most beer continues to taste perfectly fine six to nine months past its expiration date.

Does beer make you fat?

What Causes a Beer Belly? It's not necessarily beer but too many calories that can turn your trim waistline into a belly that protrudes over your pants. Any kind of calories -- whether from alcohol, sugary beverages, or oversized portions of food -- can increase belly fat.

Does alcohol lose its potency when left open?

Once you pop open the bottle, you allow air to enter, and thus begins the oxidation process, and furthermore the taste will alter, and not for the better. The good news is that most hard liquor will remain drinkable indefinitely if it remains unopened.

Can old beer give you diarrhea?

Scientists have found that drinking small amounts of alcohol tends to speed up the rate of digestion, causing diarrhea. On the other end of the spectrum, drinking large amounts of alcohol can delay digestion and cause constipation. Alcohol can also irritate your digestive tract, worsening diarrhea.

Does beer go flat after opening?

Once the beer is opened, it should be drunk within a day or two. After that time, in most cases it'll be fine, but its taste will be far from what you've expected (it'll be flat). That means that there's no sense in storing beer after opening – after two days it'll taste stale and you'll probably discard it either way.

Can you drink beer left in the sun?

Canned beer is opaque, so it is going to be completely unaffected by UV rays. Even if you left it out in the sun all day. A can of beer also captures less oxygen during the canning process, so your beer will keep longer.

Does alcohol get stronger the longer it sits?

It will give you an entirely new appreciation for the effects of aging. Unlike wines, distilled spirits do not improve with age once they are in the bottle. As long as they are not opened, your whiskey, brandy, rum, and the like will not change and they will certainly not mature further while they wait on the shelf.

Does beer expire in the fridge?

Does Beer Go Bad in the Fridge? Eventually, all beer goes bad. Your refrigerator is both cool and dark, as long as the door isn't opened too often. As mentioned above, refrigeration slows down natural aging processes and allows a beer to taste fine up for a good two years after its expiration date.

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