Glossary of Terms...
Much is spoken of the quality and intensity of dried hop aroma. These are strong varietal characteristics. There appears to be a general relationship between the type and heaviness of a hop aroma and the flavor and aromatic properties of beer.
A soft resin component, beta-acids are not bitter in the natural or isomerized form. Some of the oxidation products do provide bitterness, and the beta-acids can be chemically transformed into light stable bittering forms.
The alpha acids exist in three analogous forms, humulone, ad-humulone, and cohumulone; and the proportions of these analogues vary markedly with variety. Varieties with relatively low co-humulone levels are strongly favored.
There are certain physical properties of hop cones while unimportant in the brewing process, are strongly characteristic of a particular variety. Light loose cones are much more prone to shatter during harvesting while heavy dense cones pick beautifully as they roll well and hang together.
Varieties can display a wide range of reaction to various hop diseases. Of great importance in the U.S. are the fungal disease downy mildew and the viral disease ring-spot.
Hop varieties vary widely in structural aspects such as general vigor, lateral length, and the overall vine structure. These type of characteristics can make a variety more or less easy to pick and handle.
Hop lupulin may vary in color from pale yellow to an intense golden color. It is not known if lupulin color affects brewing performance, but it is a fairly strong characteristic of a variety. It is certain that the bitter hops have much greater quantities of lupulin than the aromatic types.
This is a statement of the time in the hop harvest season at which the particular variety reaches optimal maturity. Harvesting in the United States occurs from about August 20 to September 20.
MYRCENE, HUMULENE, CARYOPHYLLENE, FARNSENE
The four major components of the essential oils and between them they account for about 60-80% of the essential oil of most varieties. The compounds are all highly volatile hydrocarbons; and during boiling of the wort, most if not all of them, are driven off and contribute little to hop flavor and aroma in beer.
Brief remarks about the ancestry of a variety. In the case of very old varieties like Saaz or Hallertau, there is no ancestral information. We know only that this particular varietal type was selected over many years by growers and brewers in a particular area. More modern varieties can often be traced back through two to three generations of crosses often involving other known hop varieties. It is important to note that the qualities of a hop variety are only partly determined by the genes it receives.
This is another characteristic which is of direct concern to both grower and brewer. If a hop is known to pick well, one can expect a good clean sample. If a hop is difficult to pick, one is more likely to see shattered cones and a higher proportion of leaf and stem in a sample.
Oxidation of alpha acids removes their ability to be isomerized to the required bitter isomers. In comparable circumstances, some varieties lose a greater proportion of their alpha acids to oxidation than others do. Cold storage and anaerobic conditions can delay oxidation. Some oxidation of essential oil components is necessary to produce compounds thought to be important in beer flavors, so controlled aging is important for hops required for both bittering and aromatic properties.
This characteristic varies widely with seasons, varieties, and growths from 0.5 mls to about 3 mls per 100 g of hops. While the soft resin are responsible for providing the bitterness of a beer, the quantity and composition of the essential oils are responsible for the amount and quality of hop flavor and aroma in beer.
This is the kiln dry weight of hops normally produced by a variety in commercial production in the U.S. On an average, the aromatic types tend to be lower yielding and more highly priced than the bitter types.