Beer's Gone Bad: Don't Drink, Be Wary!

Beer is a beloved beverage for many, but it's important to be cautious when consuming it. Sometimes, beer can go bad, and drinking it in such a state can lead to an unpleasant experience. In the 1998 film Can't Hardly Wait, a character named William Lichter learns this the hard way, exclaiming, Nobody drink the beer, the beer has gone bad! In real life, beer can spoil due to various factors, and it's essential to recognize the signs of bad beer to avoid a disappointing or even revolting drinking experience.

How to tell if your beer has gone bad

Beer is susceptible to a long list of potential problems that can affect the way you enjoy it. It's common practice for breweries and retailers to date their products so that they know when to stop selling them. But, does beer expire?

Beer, when left at room temperature, will stay fresh for four to six months on average. If kept refrigerated, the beer can stay fresh for an additional two or three years. Beer with a 4% ABV will hold its flavour for five to nine months at room temperature and two years when stored in the fridge, while beers with an ABV of over 8% can maintain their flavour for two to three years when refrigerated.

• If you open a bottle and the beer gushes out like it's been shaken, this means it's off.
• If the aroma is sour or it tastes sour.
• You might see white patches of yeast on the surface of the liquid.
• The easiest way to tell is by checking its expiration date.
• If there is a dusty or cloudy layer at the bottom of the bottle, this indicates that yeast has formed and it's breaking down the beer.
• Changes in colour, like turning from golden to brown.
• The head dissipates quickly and leaves behind only foam.
• If your beer doesn't have as much fizz as it used to, or if there is no white foam rising right after opening a bottle, it's past its prime.
• If your beer tastes like green apple or mowed grass, this is acetaldehyde, which is present in all beers.
• If your beer tastes like buttered popcorn or butterscotch, this is diacetyl, which is caused by a bacterial infection.
• If your beer tastes like creamed corn, this is dimethyl sulfide (DMS), which is caused by a bacterial infection during fermentation.
• If your beer smells like skunk, it's lightstruck, which is caused by exposure to oxygen, heat, or light.
• If your beer tastes like cardboard, it's old and slightly oxidised.

The effects of UV radiation on beer

Ultraviolet (UV) radiation is a non-thermal disinfection technique that is gaining popularity in the food and beverage industry. The effects of UV radiation on beer are varied and depend on the specific type of beer and the conditions under which it is exposed to UV light.

Microbial Contamination

Beer is susceptible to microbial contamination, particularly by lactic acid bacteria such as *Lactobacillus brevis*, which can lead to spoilage characterised by turbidity, acidification, and the production of undesirable aromatic compounds. UV treatment has been shown to be effective in reducing microbial contamination in beer. In one study, pulsed UV light with a wavelength of 266 nm was able to achieve more than three log reductions in *Escherichia coli K12 in non-alcoholic beer when exposed to a fluence of 10 J/cm2. However, when applied to blonde ale and centennial red ale beers, the microbial reduction was lower, with log reductions of up to 4.2 and 2.4, respectively, for a treatment time of 5 minutes.

Formation of Off-Flavours

UV radiation can trigger the degradation of iso-α-acids present in beer, leading to the formation of an undesirable volatile compound called 3-methylbut-2-ene-1-thiol (3-MBT). This compound has an aroma associated with skunk spray and has a very low sensory threshold, making it easily detectable by the human nose. The formation of 3-MBT is more pronounced in lighter-coloured beers due to their higher light penetration depth. Blonde ale, for example, showed higher concentrations of 3-MBT compared to centennial red ale when treated with UV light.

Changes in Physicochemical Properties

UV treatment can also cause changes in the physicochemical properties of beer, including colour, bitterness, pH, and total soluble solids (TSS). For instance, UV treatment may affect the light degradation properties of coloured compounds in beer, such as melanoidins and polyphenols, resulting in lighter or darker colours depending on the specific beer type. Additionally, UV exposure can lead to the photo-oxidation and degradation of iso-α-acids, which can further contribute to the formation of off-flavours. The bitterness of beers may also be impacted, with some beers showing an increase in bitterness while others exhibit a decrease. Other physicochemical properties, such as pH and TSS, may also be slightly altered by UV treatment, although the changes are typically minor.

The importance of storing beer in a cool, dark place

Storing beer in a cool, dark place is essential to maintaining its freshness and preventing it from becoming "skunked." Skunked beer refers to beer that has been damaged by exposure to UV light, warm temperatures, or oxygen, resulting in a musty, "skunky" odour and a compromised flavour.

UV light, or sunlight, can cause permanent damage to beer by reacting with the hops, the main preserving ingredient. This results in what is known as light-struck or skunked beer, where a sulphur off-flavour is produced, similar to a skunk's natural defence mechanism. Even a few hours of exposure to diffuse daylight can lead to skunked beer. Therefore, it is crucial to store beer in a dark place, away from sunlight and fluorescent light.

Warm temperatures also accelerate the deterioration of beer. Heat increases the rate at which beer deteriorates and ages, and can cause the production of dimethyl sulfide (DMS), resulting in a cooked-vegetable or cooked-corn flavour and aroma. Additionally, prolonged exposure to heat can lead to the breakdown of yeast, producing a flavour and aroma similar to burning tire rubber. Thus, storing beer in a cool place is crucial to maintaining its freshness.

Oxygen exposure also affects the beer, regardless of how it is stored. Heat and motion accelerate the oxidative process, which can lead to the formation of undesirable compounds and off-flavours. Therefore, storing beer in a cool, dark place helps to minimise oxidation and preserve the intended flavour profile.

To summarise, storing beer in a cool, dark place is vital to prevent skunking, heat damage, and oxidation. By following these storage guidelines, beer enthusiasts can ensure that their beverage of choice remains fresh, flavourful, and enjoyable.

The safety of drinking expired beer

Beer is a beloved beverage for many, but what happens when it expires? Is it safe to drink, or should you toss it out?

First, let's understand what happens when beer expires. Unlike spoiled milk or mouldy bread, expired beer doesn't necessarily pose health risks. The fermentation process, low pH level, and alcohol content in beer create an environment that discourages the growth of harmful microorganisms. So, even if a sealed beer sits on the shelf for years, it's unlikely to make you sick.

However, that doesn't mean it's entirely risk-free. While it won't make you sick, expired beer can undergo flavour changes that make it taste unpleasant. Over time, beer can lose its carbonation, becoming flat and lacking the refreshing fizz you expect. Additionally, if a non-tangy or non-acidic beer develops a vinegary taste, it's a sure sign that bacteria have invaded, and it's best to discard it.

To identify if your beer has gone bad, look out for these signs:

• Loss of carbonation, resulting in a flat beer.
• A vinegary taste in beers that aren't meant to be tangy or acidic.

Now, let's address the question: is it safe to drink expired beer? The answer is yes, in most cases. Drinking expired beer won't make you sick, but it might not be a pleasant tasting experience. The worst thing that can happen is that you'll end up with a bad taste in your mouth.

To ensure the best drinking experience, it's recommended to consume beer as fresh as possible, especially for hop-heavy styles like IPAs. The volatile aromas from hops dissipate over time, and an IPA that's a few months old may have lost those delightful hop characteristics.

To summarise, while drinking expired beer is generally safe, it's not advisable if you want to enjoy the beer's flavour. Always check for signs of spoilage and follow proper storage guidelines, such as keeping beer in a cool, dark place, to prolong its freshness.

Common taste changes in old beer

Beer is a delicate, nuanced beverage that can be influenced by various factors, from brewing techniques to storage conditions. When beer goes bad, it's usually due to improper handling or ageing, resulting in undesirable flavour changes. Here are some common taste changes associated with old beer:

Diacetyl ("My Beer Smells of Butter")

Diacetyl is often referred to as brewing's "original sin" as it's present in most beers to some extent. While it can be desirable in small amounts in stouts and ales, it's typically considered a flaw in lagers. Diacetyl gives off a buttery, buttered popcorn, or butterscotch aroma and can leave a creamy sensation in the mouth. It's produced naturally during fermentation and is usually reabsorbed by yeast cells. However, high flocculating yeast, weak or mutated yeast, inadequate oxygenation, low fermentation temperatures, or short boils can result in excess diacetyl.

Dimethyl Sulphide ("My Beer Smells of Sweetcorn")

Dimethyl sulphide (DMS) can give off an aroma of sweetcorn, cooked cabbage, tomato sauce, or even shellfish. It is formed during the malting process of grains and is later converted to DMS when heated during wort production and fermentation. DMS is more prevalent in pale ales and lagers and can be desirable in some of these styles. However, excessive amounts or its presence in other beer styles can be off-putting.

Ferrous Sulphate ("My Beer Smells of Metal")

Ferrous sulphate imparts a metallic taste and smell to beer, resembling iron, pennies, ink, or even blood. It usually affects the mouthfeel but can also impact the odour. This off-flavour occurs when beer or raw materials come into contact with poor-quality metal machinery or packaging, such as metal cans, bottle caps, or kegs.

Hydrogen Sulfide ("My Beer Smells of Rotten Eggs")

Hydrogen sulfide (H2S) is produced naturally during fermentation and is present in all beers, though in varying concentrations. While it can add a "fresh" flavour at low levels, higher concentrations give off a rotten egg or sewage-like odour. Lager yeasts tend to produce more sulfur aromas, and conditioning or lagering can help reduce these sulphur smells over time.

Isoamyl Acetate ("My Beer Smells of Banana")

Isoamyl acetate is a common ester flavour in all beers, with concentrations varying across different styles. It gives off a banana or pear drop aroma and, to a lesser extent, hints of strawberry, raspberry, or grapefruit. It is a key flavour in some lagers, ales, German-style wheat beers, and Belgian ales. Underpitching or high fermentation temperatures can lead to stronger fruity flavours that may be inappropriate for certain beer styles.

Oxidation ("My Beer Smells Like Paper")

Oxidation occurs when oxygen negatively reacts with molecules in the wort or beer, often due to unnecessary splashing during transfer or excessive headspace in bottles. It results in cardboard-like or papery aromas and flavours, commonly described as tasting like stale or old wet cardboard. Lighter beers are more susceptible to oxidation, and it can be minimised by careful handling and minimising oxygen exposure.

Frequently asked questions