Beer Left Outside: Still Refreshing Or A Disaster?

Beer is a beverage that can last for months, but its shelf life depends on several factors, including temperature, exposure to sunlight, and oxygen. So, does leaving a beer outside affect its quality? The answer is yes. Sunlight, especially UV rays, can cause a chemical reaction with the essential oils in hops, resulting in a skunk-like smell and taste. This is the biggest cause of bad beer. Additionally, heat from direct sunlight can also affect the taste, although to a lesser extent than light. Oxygen exposure, such as when a beer is left open, can also cause oxidation, degrading the flavour and changing its colour. Therefore, it is recommended to store beer in a cool, dry, and dark place, minimizing temperature fluctuations and oxygen exposure, to maintain its optimal quality.

Beer exposed to sunlight

Sunlight, and the UV rays it contains, can have a detrimental effect on beer. The UV rays cause a chemical reaction with the essential oils found in hops, which leads to the creation of chemical compounds that give off a skunk-like smell. This is why beer is often described as having "gone skunky".

The darker the beer, the less likely it is to be affected by sunlight. This is because dark beers absorb a wider spectrum of light than light beers. Therefore, a Guinness will be better protected from the sun's rays than a pale beer, particularly an IPA or NEIPA.

The type of bottle or can the beer comes in will also influence how badly sunlight affects the taste. Brown glass beer bottles offer the best protection from sunlight, whereas clear glass offers no protection at all. Canned beer is opaque, so it will be completely unaffected by UV rays.

In addition to sunlight, oxygen and heat can also affect the taste of beer. An opened beer will lose a lot of flavour over time as it is exposed to oxygen. And while heat from the sun is unlikely to cause the skunk smell, very high temperatures can affect the taste of beer.

Beer exposed to oxygen

Oxygen is the enemy of beer. It can spoil the long-term stability of your beer's flavour and clarity and lead to a variety of off-flavours. The Beer Judge Certification Program (BJCP) describes oxidised beer as demonstrating "any one or a combination of stale, winy/vinous, cardboard, papery, or sherry-like aromas and flavours".

Oxygen exposure degrades lively alcohols and aromatics into bland shells of their former selves. In most cases, drinking oxidised beer is not an experience one willingly seeks.

During the early stages of yeast growth, yeast will scrub all the oxygen from the beer and use it to grow and expand. However, after the yeast has started fermentation, oxygen is considered a contaminant.

For home brewers, oxygen is most often introduced when transferring beer from one vessel to another, during the bottling or kegging process, or when beer is left out and exposed to the air. Excessive splashing during transfer, small leaks in your siphon or kegging system, or a poor seal on your bottle caps or keg can lead to excessive oxygen.

To avoid oxidation, it is recommended to minimise splashing when transferring beer from one vessel to another and to steer firmly clear of any pouring, dumping, or other bulk movement. The key is to "rack quietly".

The few beer styles that can improve with some long-term oxygen exposure are generally high in alcohol, dark in colour, and malt-focused: barley wines, old ales, imperial stouts, and so on. In these cases, melanoidins in dark beers oxidise into the characteristic flavours of sherry, which complement dark malts more than they do Pils-coloured counterparts. However, this is not a reason to intentionally introduce oxygen into your beer.

Beer temperature fluctuations

Beer is very resistant to heat and will probably not go bad at room temperature for extended periods. However, temperature fluctuations can impact beer in several ways. Firstly, if the temperature changes are extreme and frequent enough, they can cause the closure to loosen, allowing oxygen to seep in and break down the beer, making it go flat. Secondly, fluctuations can affect the flavour and chemistry of the beer. Beer that has been exposed to temperature fluctuations may taste "skunked".

However, beer is quite resilient to temperature changes. During the brewing and distribution process, beer is exposed to a wide range of temperatures numerous times. As long as the beer is kept out of direct light, it can even sit in 85-degree heat for a week and be fine a year later. For prolonged exposure, 75 degrees Fahrenheit is usually okay. In general, for every 10-degree Celsius increase in storage temperature, beer will age roughly 2-3 times faster.

Therefore, while temperature fluctuations can impact beer, especially if the changes are extreme and frequent, beer is relatively resilient and can withstand some changes in temperature without significant adverse effects.

Beer's shelf life

Beer does indeed have a shelf life and will eventually go bad. As a general rule, beer stored at room temperature will last for around six to nine months beyond its use-by date, while refrigeration can increase this to up to two years. However, it's important to note that several factors can affect the shelf life of beer.

Firstly, beer is susceptible to microbial infection and non-biological instability, including physical or haze, flavour, foam, gushing, and light issues. The latter is a significant concern, as ultraviolet (UV) light can cause a chemical reaction in hops, one of the key ingredients in beer, resulting in an unpleasant smell and taste. This is why brewers often use darker bottles or cans, which offer more protection from UV light.

Secondly, oxidation can alter the flavour and aroma of beer. Oxygen interacts with the chemical compounds in the beer, causing different flavours to develop, such as diacetyl, which adds a buttery taste. Bottled beers may be more prone to oxidation due to air leakage, while cans have a tighter seal.

Thirdly, temperature fluctuations can affect the quality of beer. While beer can be safely exposed to a range of temperatures during brewing and distribution, extreme temperatures or frequent changes can accelerate the ageing process and impact flavour.

Finally, the type of beer and its ingredients can also determine its shelf life. Beers with additional ingredients, such as fruit or honey, may have a shorter shelf life or be more sensitive to temperature changes. On the other hand, the alcohol content in beer acts as a natural preservative, as microbes cannot survive in high alcohol concentrations.

To maximise the shelf life of beer, it is recommended to store it in a cool, dark place, preferably a refrigerator, and to keep the bottles or cans upright to minimise the surface area exposed to oxygen.

Beer bottles vs cans

The age-old debate of beer bottles versus cans has many factors to consider, including taste, convenience, and environmental impact.

Firstly, when it comes to taste, the answer is neither. Beer tastes better when poured into a glass, as drinking from the bottle or can limits your sensory experience. However, if you must drink straight from the container, cans are generally better at preserving taste. Beer in clear or green glass bottles can be affected by UV light, causing an unpleasant "skunky" taste. Brown bottles offer better protection, but cans provide the best defence against skunkiness. Some people also claim that beer from a can has a metallic taste, but this is likely due to smelling the can while drinking. Brewers have lined cans with food-safe plastic since the 1930s to prevent metallic flavours.

Convenience is another factor to consider. Glass bottles are heavy and fragile, making them less ideal for travel and outdoor activities. They also usually require a bottle opener. In contrast, aluminium cans are lightweight, durable, and easy to open.

Finally, when it comes to environmental impact, both bottles and cans can be environmentally friendly if recycled. Glass is made from recycled materials and silica, giving it a smaller environmental footprint initially. However, aluminium is more likely to be recycled and has a longer life cycle. Additionally, glass is heavier and requires more fuel for transportation. So, while glass may be better for the environment in terms of production, aluminium may be better when it comes to sustainability and recycling.

In conclusion, while there are valid points on both sides of the debate, cans seem to come out on top in terms of taste preservation, convenience, and environmental impact, provided that they are recycled. However, the best way to enjoy beer is by pouring it into a glass to get the full sensory experience.

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