2009_Book_FoodChemistry

20.1 Beer 895
Table 20.2. Production of hops in 2006 (1000 t)
Continent Hops Country Hops
World 129 Germany 34
USA 26
Africa 23 Ethiopia 23
America, Central – China 22
America, North 26 Czech Rep. 5
America, South Poland 3
and Caribbean – UK 2
Asia 25 Korea 2
Europe 53 Slovenia 2
Oceania 2 Spain 1
Australia 1
France 1
Albania 1
∑ (%) a 98
a World production = 100 %.
the bitter substances. In fresh hops they occur
mostly in the form of α-acids (cf. Formula 20.1):
humulon (I), cohumulon (II), adhumulon (III);
andintheformofβ-acids: lupulon (IV), colupulon
(V) and adlupulon (VI). These compounds are
susceptible to changes during drying, storage and
processing of hops. The changes usually involve
isomerization, oxidation and/or polymerization.
As a consequence, a great number of secondary
products are found.
hardy, perennial climbing vine. The flowers of the
female plants, though lacking pollination, grow
well and cluster into a conical blossom which has
large thin scales or bracts. This cone, when ripe,
is harvested and used commercially. The plant is
propagated vegetatively by planting cuttings from
fleshy roots. The hop cones are picked in August
or September and are dried and pressed into bales.
The lupulin gland in the upper and lower portion
of bracts contains, in addition to essential oils, bitter
constituents. Data on hop production are given
in Table 20.2.
20.1.2.3.2 Composition
Table 20.3 presents data on the composition of
hops. The constituents of utmost importance are
Table 20.3. Composition of hops
Constituent Content Constituent Content
(%) a (%) a
Bitter compounds 18.3 Crude fiber 15.0
Essential oil 0.5 Ash 8.5
Polyphenols 3.5 N-free extract-
Crude protein 20.0 able mater 34.0
a As % dry matter; moisture content approx. 11%.
(20.1)
The quality and intensity of the bitter taste
derived from these secondary products are
different. Evaluation of hops is therefore based
on a determination of composition of individual
α- andβ-acids, rather than of the total content
of bitter substances. As seen in Table 20.4,
the composition varies greatly with hop origin.
During the boiling of hops, humulons isomerize
into isohumulons (cis-compounds, VII;
trans-compounds, VIII; cf. Formula 20.2),
which are more soluble and bitter than the
initial compounds. The isohumulons can be
further transformed into humulinic acids (IX,X),
which have only about 30% of the bitterness of
isohumulons.
Hulupons (XI) and luputrions (XII) are the secondary
products of the lupulons. They possess
an exceptionally pleasant and mild bitter taste
which is much less bitter than the compounds
from which they are derived. Hence the bitter
taste of beer is primarily due to compounds of the
humulon fraction.