2009_Book_FoodChemistry

902 20 Alcoholic Beverages
Thus, for example, if the solids content (E) of
a beer is 3% (w/v) and the alcohol content (A)
is 5.0% (v/v), then the solids content of the wort
before fermentation was 12.6% (w/v). The stemwort
content in Germany is 2–5.5% for plain
beers, 7–8% for draft beers, 11–14% for full beers
and above 16% for strong beers.
20.1.7.3 Acids
Carbon dioxide is responsible to a substantial
extent for the refreshing value and stability of
beer. CO 2 is 0.36–0.44% in bottom fermented
beers, while in Weiss beer the CO 2 content is
up to 0.6–0.7%. A CO 2 content below 0.2%
gives flat and dull beers. Apart from small
amounts of lactic, acetic, formic, and succinic
acids, beer contains 9,10,13- and 9,12,13-trihydroxyoctadecenoic
acid. In fact, 9.9±2.1mg/l
were found in five types of beer and 9(S), 12(S),
13(S)-trihydroxy-10(E)-octadecenoic acid was
the main compound and accounted for 50–55% of
the 16 stereoisomers. The pH of beer is between
4.7 (dark, strong beer) and 4.1 (Weiss beer).
20.1.7.4 Nitrogen Compounds
The N-compounds in beer (0.15–0.75%) originate
primarily from proteins in the raw materials
and from yeast. They consist mainly of proteins
plus high molecular weight protein degradation
products; both being responsible for cloudiness
in beer during cold storage. The free amino acids
found in malt are also present in beer. It appears
that glutamic acid contributes to beer taste. The
presence of volatile amines has also been confirmed.
20.1.7.5 Carbohydrates
The carbohydrate content is approximately
3–5%, while in some strong beers or malt beers
it may be considerably higher. Pentosans are
also present in addition to dextrins, mono- and
oligosaccharides (maltotriose, maltose, etc.).
Glycerol normally is 0.2–0.3% of beer.
20.1.7.6 Minerals
Minerals make up 0.3–0.4% of beer and consist
mostly of potassium and phosphate. Calcium,
magnesium, iron, chloride, sulfate and silicates
are also present.
20.1.7.7 Vitamins
Vitamins of the B-group (vitamins B 1 and B 2 ,
nicotinic acid, pyridoxine and pantothenic acid)
are present in various beers, often in significant
amounts.
20.1.7.8 Aroma Substances
The odorants, e. g., for Pilsener beer are shown in
Table 20.6. The aroma is reproduced by a suitable
mixture of these substances dissolved in water,
the pH of which is adjusted to 4.3 with carbonic
acid. This emphasizes the fact that the key odorants
of this type of beer can be analytically identified.
(R)-Linalool and ethyl-4-methylpentanoate
are derived from hops and pass into the beer on
boiling the wort.
The odor- and taste-active substances essentially
determine the type of beer. The bitter taste of
Pilsener beers is produced by relatively high concentrations
of isohumulons, and humulenes (including
oxidation products), while larger amounts
of furaneol are responsible for the caramel note of
dark beers.
In the production of alcohol-free beer, the concentrations
of important aroma substances drop
(Table 20.7).
20.1.7.9 Foam Builders
The foam building properties of beer are due to
proteins, polysaccharides and bitter constituents.
The β-glucans stabilize the foam through their
ability to increase viscosity. Addition of semisynthetic
polysaccharides, e. g., propyleneglycol alginate
(40 g/hectoliter), to beer provides a very
stable foam although the addition is judged as unfavorable.