Light is the enemy of beer
One critical factor that must be considered when buying beer is preservation. Anyone who has toured a brewery has noted the complexity, effort, and creativity put into the making of beer. It is a crying shame that many retailers ruin otherwise excellent beers by improper storage.
Beer is a natural, ‘living’ product (like milk) and strict preservation and storage standards are essential to keeping it fresh and flavorful. The two most common factors affecting beer preservation are light exposure and spoiling. Beer that has been exposed to excessive light may develop a ‘skunky’ odor. This is caused as wavelengths of light penetrate the beer, causing photochemical changes within it. Many breweries use brown and green glass to protect their beers from specific light wavelengths, but this really is not enough. Note that beer is prey both sunlight and artificial forms of light such as fluorescent lighting found in retail sores and warehouses.
Do not buy beer that has been stored in direct contact with light!