Hops

The hop plant is a tall, climbing plant, distantly related to the cannabis plant, the nettle, and the elm. Hop cones, used in brewing, are only produced by the female plant beginning around July. The hop cone is formed from petals, and on the inside of the petals is where the lupulin is formed. The volatile oils in the lupulin are what is used to flavor and preserve beer. The hops are harvested in September, then dried before they are used in brewing.

Hops add a bitter flavor to beer as well as a pleasant aroma. They also prevent beer spoilage from certain micro-organisms, and enhance the foam on beer. Most hops sold in homebrew shops are rated by the Alpha Acid percentage. This number is measured by their weight versus the weight of the whole flower. So an AAU of 6% means that 6% of the weight of the hop is alpha acid resins. These resins are not water soluble and must be boiled for the resins to dissolve.

There are some hops that are called bittering hops, and others are called aroma hops. Bittering hops are boiled along with the wort the entire length of the boil. They yeild all of their flavor to soften the sweetness of the malt. Examples of bittering hops are Brewers Gold, Centennial and Galena. Their Alpha Acid percentage can range from 6-14%.

Aroma hops are only boiled a short while and lend, somewhat obviously, their aromas to beers. The shorter these are boiled, the more aromatic the beer. Their AA percentage ranges from 2 to 8%. Some aroma hops are Kent Golding, Cascade, Mount Hood, and Fuggles. Some Aroma hops are so connected with beer they are called Noble Hops. These are usually the best for lagers. There are only four Noble Hops: Hallertauer Mittelfrüh, Tettnanger Tettnang, Spalter Spalt, and Czech Saaz.

Since alpha acids can vary from batch to batch of a specific hop, some recipe writers use Home Brewing Units to indicate how much hops should be used. (See my previous post).