When beer is stored in transparent bottles, sunlight penetrates into the bottle and leads to the decomposition of some structures inside the beer that has been exposed to sunlight for a long time. As a result of these reactions, the taste of beer deteriorates, and it starts to smell "skunky," therefore, beer taste is characterized as the smell of a skunk.
The sensitivity of beer to light is the reason for a critical, challenging shelf-life problem for the beer industry and is the main reason for storing beer in dark-colored containers.