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AGRONOMICS
MATURITY:
This is a statement of the time in the hop harvest season at which
the particular variety reaches optimal maturity. Harvesting in the
U.S. occurs from mid August to the end of September.
YIELD:
This is the kiln dry weight of hops normally produced by that
variety in commercial production in the U.S. On average, the aromatic
types tend to be lower yielding and more highly priced than the
bittering types.
DISEASE
REACTION:
Different varieties can display a wide range of reaction to various
hop diseases. Of great importance in the USA are the fungal disease
downy mildew and the viral disease ring spot.
PICKABILITY:
This is another characteristic which is of direct concern to both
grower and brewer. If a hop is know to pick well, one can expect
a good clean sample. If a hop is difficult to pick, one is more
likely to see shatterd cones and higher proportion of leaf and
stem in a sample.
BREWING
QUALITIES CONE STRUCTURE:
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.
AROMA:
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.
ALPHA
ACIDS:
A major component of the soft resins. When isomerised, these materials
provide the main bitter compounds associated with beer. The alpha
acid content varies widely among hop varieties from levels of
3-4% in aromatic type hops to levels of 13-14% in the bitter hops.
BETA
ACIDS:
A soft resin component, beta-acids are not bitter in the natural
or isomerised form. However, some of the oxidation product does
provide bitterness, and the beta-acids can be cheically transformed
into light-stable bittering forms.
CO-HUMULONE:
The alpha acids exist in three analogous forms, humulone, ad-humulone,
and co-humulone; and the proportions of these analogues vary markedly
with variety. It is widely held that relatively high levels of
co-humulone produce a harsh, unpleasant bitterness and have a
negative impact on head retention. Although this belief is still
being questioned, varieties with relatively low co-humulone levels
are still strongly favored.
Storability:
Oxidation of alpha acids removes their ability to be isomerised
to the required bitter isomers. In comparable circumstances, some
varieties lose a greater proportion of their alpha acids to oxidation
than other do. Cold storage and anaerobic conditions can delay
oxidation. Some produce compounds thought to be important in beer
flavors, so controlled aging is important for hops required for
both bittering and aromatic properties.
TOTAL
OIL:
This characteristic varies widely with seasons, varieties, and
growth from 0.5 mls to about 3 mls per 100 g of hops. While the
soft resins 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.
MYRCENE,
HUMULENE, CARYOPHYLLENE,
AND FARNESENE:
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
so contribute little to hop flavor and aroma in beer.
LUPULIN:
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 aroma types.
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