Beer can go bad quickly when exposed to sunlight and heat. The hot sun causes the flavors to deteriorate and makes the beer taste stale or skunky. There are a few factors that determine how long beer lasts before going bad in the sun.
Does Beer Go Bad In The Sun?
Yes, beer can definitely go bad when left out in the sun. The ultraviolet rays and heat from sunlight can cause chemical reactions in the hops and malt that make beer taste unpleasant. Exposure to light causes a few issues that can ruin beer:
- Lightstruck flavors – Sunlight interacting with hops causes a skunky/sulfur-like off-flavor.
- Loss of hop aroma – The aromas from hops break down in light.
- Oxidation – Heating and light accelerate oxidation which leads to stale flavors.
These chemical changes happen faster at higher temperatures. So a beer left out on a hot, sunny day will deteriorate quicker than one left in cooler, shaded conditions.
How Long Does Beer Last In The Sun?
An opened beer can go bad in as little as 15 minutes when left in direct sunlight on a hot day. In cooler conditions, it may last 1-2 hours before undesirable flavors develop. Unopened beers fare better, but the taste still suffers after several hours in the sun.
Here’s approximately how long different types of beer will last in sunlight before the taste suffers noticeably:
| Beer Type | Hot Sunny Day (90°F+) | Cool/Overcast Day (70°F) |
|---|---|---|
| Opened beer | 15 min – 1 hour | 1 – 2 hours |
| Unopened beer (bottles) | 2 – 3 hours | 4 – 6 hours |
| Unopened beer (cans) | 4 – 6 hours | 6 – 8 hours |
These times can vary based on the exact conditions. But it illustrates how quickly sunlight can ruin the taste of beer.
Why Does Sunlight Make Beer Go Bad?
There are two main reasons that sunlight damages beer flavor:
- Ultraviolet rays – UV rays interact with hop compounds called isohumulones, breaking them down into free radicals that cause skunky, sulfur-like flavors.
- Heat – Sunlight heats up the beer, accelerating chemical reactions that stale the flavor.
Hops are very sensitive to light. Even visible light can cause the degradation of aromatic hop oils that give beer its fresh taste. Heating speeds up damaging oxidation reactions as well.
UV Rays and Skunky Flavors
The number one problem caused by sunlight is “lightstruck” flavors. These skunky, sulfury flavors are the result of UV rays breaking down hop compounds.
Isohumulones found in hops are degraded into free radicals that quickly combine with sulfur compounds already present in beer. This reaction forms molecules nearly identical to the thiols responsible for skunks’ foul spray. Even tiny amounts of these “skunky thiols” can overwhelm the beer’s flavor.
This photochemical reaction can occur very quickly. Pale lagers and IPAs with more hops are especially vulnerable. Just a minute of sun exposure can start producing noticeable skunky flavors.
Oxidation
Heating and sunlight also accelerate oxidation reactions in beer. The heat provides energy for oxygen to react with compounds like fatty acids, alcohols, proteins, and sugars in the brew.
This forms “stale” flavors resembling cardboard, wet paper, apples, or sherry-like aromas. Hop oils that provide fresh aromas are also quickly destroyed by oxidation.
Even cool fluorescent lighting can warm beer enough to gradually cause staling. But direct sunlight can heat beer by dozens of degrees in just minutes, greatly hastening oxidation.
Does Beer Go Bad In The Sun Faster In Bottles Or Cans?
Canned beer withstands sun exposure better than bottles. The difference lies in how the packaging blocks wavelengths of light.
Glass blocks little UV light – Standard brown glass blocks only 30-40% of incoming UV rays. So a significant amount still reaches the beer, causing skunky flavors.
Cans completely block UV – Aluminum cans prevent all UV light from hitting the beer, protecting the hop aromas and preventing skunking.
However, both cans and bottles allow heat from the sun to warm the beer, accelerating oxidation. So neither offers complete protection.
One study exposed canned and bottled beer to direct sunlight for 6 hours on a 79°F day. The canned beer only showed noticeable oxidation-related stale flavors. But the bottled beer developed significant skunky flavors in that short time.
So while both can go bad when heated, glass bottles also permit the lightstruck reactions. For maximum sun protection, choose canned beer or bottles that specifically block UV rays.
Tips To Prevent Beer From Going Bad In The Sun
You can’t stop sunlight from damaging beer entirely. But there are some tips to help slow the process:
- Store unopened beer indoors – Keeping beer out of light until you’re ready to drink it is best.
- Use cans or UV-blocking bottles – Cans prevent skunking; “amber” bottles block more UV.
- Wrap in towels or koozies – Insulate and block light exposure for opened drinks.
- Use opaque cups – Don’t drink from clear plastic cups; use cups that block light.
- Stay in the shade – Seek shade to keep sunlight off opened beer.
- Drink ASAP – Once opened, try to finish beers within an hour or less.
Avoid leaving beers sitting out in direct sun whenever possible. But if you do, wrap them up or finish drinking quickly to limit the light and heat damage.
How To Tell If Beer Has Gone Bad In The Sun
Checking the taste and aroma is the best way to tell if beer has been “lightstruck” or oxidized from sun exposure. Look for these off-flavors:
- Skunky – Similar to the smell of skunk spray. May smell sulfury, medicine-like, or weed-like.
- Stale – Lacking freshness. Cardboard, wet paper, apple, or sherry aromas.
- Soapy – Caused by oxidation of hop oils.
- Metallic – From degraded lipids.
The beer may also lose its head retention and appear darker than normal. Advanceed oxidation can even cause flavors resembling sherry or vinegar.
If you notice beer smells or tastes “off” after sitting out, it has likely gone bad from sun exposure. The hoppy aromas will disappear as lighter flavors like grain and malt become more prominent.
Does Temperature Matter?
Yes, temperature dramatically impacts how quickly beer goes bad in the sun. Warmer weather causes much faster deterioration.
At higher temperatures, UV light is more intense and chemical reactions proceed faster. Even cool or cloudy days can warm beer into the 60s or 70s (°F), causing noticeable flavor changes in just 1-2 hours.
A hot summer day can heat beer well over 100°F in the sun, damaging the flavor in less than an hour. The table below shows estimated times for beer to develop off-flavors at different temperatures:
| Temperature | Opened Beer | Unopened Beer |
|---|---|---|
| 70°F (Cloudy day) | 1-2 hours | 3-5 hours |
| 80°F (Warm sunny day) | 30-60 minutes | 1-3 hours |
| 90°F (Hot summer day) | 15-30 minutes | 1-2 hours |
| 100°F+ (Extreme heat) | 5-15 minutes | 30-90 minutes |
The hotter the beer gets, the quicker sunlight, heat, and oxygen can damage the flavor. Even a few degrees temperature difference has a big impact.
Does Beer Type or Color Matter?
Yes, some beers are more vulnerable to sun damage than others. In particular:
- Pale lagers – The most sensitive to skunking because they are often packaged in clear glass.
- IPAs – Contain more hop oils and isohumulones that break down.
- Pilsners – Light color shows effects of oxidation more quickly.
- Strong ales – Higher alcohol and malt flavors help mask sun damage.
Lighter, hoppy beers without strong malt backing suffer the most. Thick, dark beers better shield themselves from deterioration.
But given enough exposure, sunlight will damage any type of beer. Certain styles just highlight the flaws sooner.
Does Bottle Color Matter?
Yes, darker bottle glass helps block more UV rays from reaching the beer. Here’s how different bottle colors compare:
- Clear glass – 0% UV blocked
- Green glass – 30-40% UV blocked
- Amber glass – 60-70% UV blocked
- Brown glass – 80-90% UV blocked
While no glass blocks UV completely, brown bottles help slow the skunking reaction substantially. Green and clear bottles offer very little protection.
However, glass color only affects UV light. All bottles still allow heat and visible light to pass through and stale beer. For full sun protection, opaque cans or cans in boxes are best.
Does Alcohol Percentage Matter?
Generally, yes. Stronger beers with higher alcohol tend to withstand sunlight better.
Higher alcohol levels help stabilize beer against oxidation and free radical formation from UV exposure. The bolder flavors from extra malt and sugars also help mask any off-flavors.
One study found that for beers aged in sunlight:
- 6% ABV – Noticeable oxidation in 6-8 weeks
- 9% ABV – Oxidation took 10-14 weeks to detect
So while no beer is immune to sun damage, stronger beers can buy you a little extra time.
Does Beer Get Skunked In The Fridge?
No, refrigerated beer does not get lightstruck or skunked. The cool temperature slows down the photochemical reactions behind skunking.
Studies show lagers stored in clear glass at 40°F for several months showed no increase in lightstruck compounds compared to beers in cans or brown glass.
However, the fridge won’t stop oxidation completely over time. So fridge-stored beer can still slowly go stale, but not skunky.
The minimal heat and UV exposure in the refrigerator means beer can stay fresh for many months when kept cold and dark. Just avoid constantly opening the door to limit oyxgenation.
Will Colder Temperatures Slow Sun Damage?
Yes, colder temperatures will dramatically slow the deterioration from sun exposure.
Cooling beer down lessens chemical reaction rates, reduces UV intensity, and limits heat saturation. While no outdoor temperature can prevent sun damage entirely, lower temps help.
Some ways to keep beer colder in the sun include:
- Use cooler with ice
- Wrap in wet towel
- Use freezer packs
- Add ice to opened cans/bottles
The longer beer can be kept below 70°F, the less quickly it will go bad. But once opened, it still needs to be consumed quickly.
Does Beer Go Bad In The Sun Faster In Cans Or Bottles?
Canned beer withstands sun exposure better than bottles. The difference lies in how the packaging blocks wavelengths of light.
Glass blocks little UV light – Standard brown glass blocks only 30-40% of incoming UV rays. So a significant amount still reaches the beer, causing skunky flavors.
Cans completely block UV – Aluminum cans prevent all UV light from hitting the beer, protecting the hop aromas and preventing skunking.
However, both cans and bottles allow heat from the sun to warm the beer, accelerating oxidation. So neither offers complete protection.
One study exposed canned and bottled beer to direct sunlight for 6 hours on a 79°F day. The canned beer only showed noticeable oxidation-related stale flavors. But the bottled beer developed significant skunky flavors in that short time.
So while both can go bad when heated, glass bottles also permit the lightstruck reactions. For maximum sun protection, choose canned beer or bottles that specifically block UV rays.
Conclusion
Sunlight can quickly damage beer flavor due to UV rays and heat. Within hours, beer can develop unpleasant skunky, stale flavors.
Pale, hoppy beers in clear glass bottles are most vulnerable. But all beer left in the sun too long will be affected.
For best results, store beer out of direct sun and finish drinking any opened containers within an hour or less. Seek shade, use koozies and coolers, and choose cans or UV-blocking bottles to limit lightstruck reactions.
With a little care, you can still enjoy beer outdoors on sunny days. Just be vigilant about any temperature changes or prolonged light exposure to keep that brew tasting its freshest.
