2009_Book_FoodChemistry

906 20 Alcoholic Beverages
Table 20.8. Main characteristics of the odor and taste of various types of beer
Flavor group
Intensity a
Munich Pilsner Pale ale US lager Stout b Lambic
Bitterness 3–6 6–10 5–8 2–4 6–10 3–6
Alcoholic flavor 2–4 3–4 3–4 3–5 3–5 3–6
Carbonation 3–4 3–4 1–3 4 3–4 3–5
Hop character 2–6 6–10 5–8 0.5–4 6–10 3–6
Caramel flavor 4–8 0.5–2 3–5 0.5–1 6–100 1–3
Fruity/estery flavor 1–2 1–1.5 1–2 2–3 2–3 3–5
Sweetness 2–3 1–2 1–2 2–3 1–2 1–2
Acidity 1–2 1–2 1–2 1–2 2–3 3–20
Cabbage-like 1–2 1–3 0.2–0.8 1–3 0.2–0.8 1–10
a Semiquantitative values on the basis of aroma values.
b Top fermented English strong beer with a stemwort content of up to 25%.
2-buten-l-thiol (cf. Table 5.5). This substance becomes
unpleasantly noticeable at concentrations
higher than 0.3µg/l. It is one of the characteristic
aroma substances below this concentration.
Enzymatic peroxidation of lipids contained in the
wort and nonenzymatic secondary reactions during
wort boiling give rise to the aroma defects
listed as No. 8 in Fig. 20.3.
A sweetish off-flavor formed during storage
of beer is caused by an increase in 3-methylbutanal,
methional, phenylacetaldehyde, ethyl
methylpropanoate and ethyl 2-methylbutanoate.
The addition of ascorbic acid or glucose oxidase/catalase
(cf. 2.7.2.1.1) is recommended to
overcome color and flavor defects caused by oxidation.
Therefore, low-oxygen bottling is of great
importance. Bottled beer should not contain more
than 1 mgO 2 /l.
Unwanted carbonyl compounds, which can produce
an off-flavor in stored beer, are bound by sulfite
derived from yeast metabolism. Yeast reduces
the sulfate present in the wort to sulfite and sulfide,
which is then consumed in the biosynthesis
of sulfur-containing amino acids. If the growth of
yeast comes to a standstill, excess sulfite is eliminated,
increasing the stability of the beer to oxidative
processes.
The very potent aroma substance 3-methyl-3-
mercaptobutyl formate (cf. 5.3.2.5) can produce
an off-aroma called “catty” (0810 in Fig. 20.3).
The concentration of phenylacetaldehyde can
also increase to such an extent on the storage
of beer that it becomes noticeable in the
aroma.
On storage, beer can become cloudy and form
a sediment. Proteins and polypeptides make up
40–75% of the turbidity-causing solids. They
become insoluble due to the formation of intermolecular
disulfide bonds, complex formation
with polyphenols, or reactions with heavy metals
ions (Cu, Fe, Sn). Other components of the
sediment are carbohydrates (2–25%), mainly
α- andβ-glucans. For measures used to prevent
cloudiness, see 20.1.8.5. Undesirable microorganisms,
e. g., thermophilic lactic acid bacteria,
acetic acid bacteria (Acetobacter, Gluconobacter)
and yeasts, can cause disturbances and defects
in various process steps (mashing, fermentation,
finished product).
20.2 Wine
20.2.1 Foreword
Wine is a beverage obtained by full or partial
alcoholic fermentation of fresh, crushed grapes
or grape juice (must). The woody vine grape
has thrived in the Mediterranean region since
ancient times and Italy, France and Spain are
still among the leading wine-producing countries
in the world. Other major producers are USA,
Argentina, Chile, Germany and South Africa.
Table 20.9 provides data on wine production and
consumption in some countries. An overview of
the individual process steps in wine production is
presented in Fig. 20.4.