What is Skunked Beer?

Skunked beer is a term used to describe beer that has been exposed to light and has undergone a chemical reaction, resulting in a distinct unpleasant odor and taste. The term “skunked” is derived from the smell of a skunk, as the odor of the beer resembles that of the animal’s spray.

The chemical reaction that causes skunking in beer is due to the interaction between the hops in the beer and ultraviolet light. When beer is exposed to light, the hops break down and release compounds that react with sulfur-containing amino acids in the beer, resulting in the formation of 3-methyl-2-butene-1-thiol (MBT), which is responsible for the skunky odor.

Skunking can occur in any beer that is exposed to light, but some beer styles are more susceptible to skunking than others due to their hop content and packaging. For example, clear or green bottles are more likely to allow UV light to penetrate the beer, resulting in skunking. In contrast, brown bottles or cans offer better protection against light exposure and reduce the likelihood of beer becoming skunked.

Understanding Skunked Beer

Skunked beer is a term used to describe beer that has been exposed to ultraviolet (UV) light or artificial light, causing it to develop an unpleasant aroma and flavor that resembles the secretions of a skunk.

This off-flavor is a result of a specific chemical reaction that occurs when the light interacts with the hops in the beer.

When beer is exposed to UV light, the isohumulones in the hops break down and react with sulfur-containing compounds, such as mercaptans, to create a new compound called 3-methyl-2-butene-1-thiol (MBT). This compound is responsible for the skunky aroma and flavor in beer.

The intensity of the skunky aroma and flavor depends on the amount of MBT that is produced, which in turn depends on the amount of UV light exposure and the type of hops used in the beer. Beers that are heavily hopped and have a high alpha acid content are more susceptible to skunking.

It is important to note that not all off-flavors in beer are caused by skunking. Other factors, such as improper storage, contamination, or aging, can also lead to off-flavors and aromas in beer. However, skunking is a common problem that can be easily prevented by storing beer in a cool, dark place away from UV light sources.

Chemistry Behind Skunking

Chemical Reaction

Skunking is a term used to describe the unpleasant taste and smell that can occur in beer when it is exposed to ultraviolet light.

The chemical reaction that causes skunking is known as a photochemical reaction. This reaction occurs when the ultraviolet light interacts with the hop compounds in the beer.

Hop Compounds

Hops are an essential ingredient in beer. They are responsible for giving beer its unique flavor and aroma. Hop compounds are made up of a variety of different chemicals, including alpha acids, beta acids, and essential oils.

Iso-Alpha Acids

The chemical responsible for skunking beer is called 3-methyl-2-butene-1-thiol, or MBT. MBT is formed when the iso-alpha acids in the hops react with ultraviolet light. Iso-alpha acids are formed when alpha acids in the hops are boiled during the beer-making process.

When the beer is exposed to ultraviolet light, the iso-alpha acids break down and react with sulfur-containing amino acids in the beer to form MBT. MBT has a strong, unpleasant odor that is similar to the odor of skunk spray. This is why skunked beer is often described as having a skunky smell.

Temperature and Skunking

Temperature Changes

Temperature changes can affect the taste of beer. Contrary to popular belief, taking a beer from cold to warm and back to cold does not skunk beer.

According to Beer Chronicle, this is a myth. However, temperature changes can cause other problems such as affecting the carbonation and head retention of the beer.

Refrigerated Beer

Refrigerating beer can help prevent skunking. Keeping beer in the dark, cool environment of a fridge can help prevent lightstruck beer. According to Cook’s Illustrated, the real culprit of off-tasting beer is light exposure. Beer that has been exposed to artificial or UV light can undergo a chemical reaction that produces an unpleasant, bitter taste. This process is called skunking.

It’s important to note that even refrigerated beer can still be skunked if it is exposed to light. Therefore, it’s best to keep beer in a dark place, such as a fridge or a cellar. Additionally, it’s important to store beer upright, as storing it on its side can cause the beer to oxidize and develop off-flavors.

Different Beer Types and Their Vulnerability to Skunking

Skunking is a phenomenon that can affect all types of beer. However, some beer types are more vulnerable to skunking than others.

In this section, we will explore the different beer types and their vulnerability to skunking.

American Lager

American lagers are a popular type of beer in the beer world. They are light-bodied, crisp, and refreshing. They are also one of the most vulnerable beer types to skunking. This is because they are often packaged in clear or green bottles, which do not offer much protection against UV rays. As a result, American lagers can become skunked very quickly, especially if they are exposed to sunlight or fluorescent light.

Pale Ales

Pale ales are another popular type of beer in the craft beer world. They are known for their hoppy and bitter flavors. Pale ales are less vulnerable to skunking than American lagers. This is because they are often packaged in brown bottles, which offer some protection against UV rays. However, if they are exposed to sunlight or fluorescent light for an extended period of time, they can still become skunked.

IPAs

IPAs, or India Pale Ales, are a type of pale ale that is known for its strong hoppy flavor. Like pale ales, IPAs are less vulnerable to skunking than American lagers. This is because they are often packaged in brown bottles, which offer some protection against UV rays. However, if they are exposed to sunlight or fluorescent light for an extended period of time, they can still become skunked.