Every wine connoisseur can tell the quality of a wine from its aroma; why would that be any different for beer. Anyone who has ever opened a beer remembers that fresh scent. Was it Fruity? Flowery? Piney? Hops are what give a beer its unique personality, its flavor, its bitterness.
Hops aren’t just about flavor and aroma, they also serve an important role in the production and preservation of beer. Hops help to stabilize the head on a beer and allow it to stick to the glass and hold its consistency. It’s also critical in the shelf life of beer; hops provide α-acids and β-acids that provide a resistance to microbacterial infections that can give beer an of taste.
α-Acids are a natural occurring class of acids found in the resin glands of the Hop flower. These are some of the most important components of beer as they give the characteristic bitterness of beer. They also bestow a resistance to microbacterial (bateriostatic) on the beer; this helps to prolong the shelf life of beer.
α-Acids must be extracted from the hops and isomerize in order to give a beer its distinctive bitterness. This usually take 60 minutes of boiling within the wort (unhopped, unfermented beer), hence why bittering hops and usually added at the start of a boil.
There 5 α-acids in beer:
Brewers are generally only interest in the Humulones and Cohumulons; humulones bestow a soft bitterness while the cohumulones bestow a harsher bitterness. Brewers usually work to achieve a ratio between the 2 to personalize their beers.
There isn’t too much that can be said about β-acids as they are unwanted in the brewing and aging process. The only thing that β-acids seem to do is contribute to long term bitterness preservation. While α-acids breakdown soon after their extraction (slowly reducing bitterness), β-acids actually contribute to bitterness as they oxidize slowly.