2009_Book_FoodChemistry

20.2 Wine 915
Table 20.14. Quality levels and natural minimum alcohol
content of German wines
Quality level
Minimum alcohol content a
Zone A b Zone B b
Table wine 5.0 6.0
Country wine 5.5 6.5
Quality wine 7.0 c 8.0
Quality wine with vintage
- Cabinet 9.5 d 10.0
- “Spaetlese” 10.0 11.4
- “Auslese” 11.1 13.4
- “Beerenauslese” 15.3 17.5
- Ice wine 15.3 17.5
- “Trockenbeeren” 21.5 21.5
a in % vol.
b Vine growing areas: Germany without Baden
(Zone A), Baden (Zone B).
c Partly 6.0.
d Partly 9.0.
100 mg/l) and stachyose (ca. 150 mg/l). Pectins
(0.12–0.15%) and small amounts of pentosans
are present.
20.2.3.3.2 Acids
The major acids of must are L-tartaric and
L-malic acids. Succinic, citric and some other
acids are minor constituents. In a good vintage,
tartaric acid is 65–70% of the titratable acidity,
but in years when unripe grapes are fermented,
its content is only 35–40% and malic acid
predominates. The good vintage year of 1911, for
example, yielded grapes with 3.1g/l malic acid
and 6.4g/l tartaric acid; in the inferior vintage
year of 1912, on the other hand, malic acid was
10.7g/l and tartaric acid 6.0g/l.
wine are traditionally defined through the must
weight, e. g., ( ◦ Oe): Cabinet (70–73), “Spaetlese”
(85–90), “Auslese” (92–100), “Beerenauslese”
(120). Internationally, the natural alcohol content
is a characteristic feature of quality. The corresponding
values for German wine are presented
in Table 20.14.
Since the density of the must is primarily dependent
on the sugar content c, it can be estimated
using the following equation:
c[%]=(0.25 × ◦ Oe) − 3 (20.7)
Hence, a must of 100 ◦ Oe contains about 22%
sugar.
20.2.3.3.1 Carbohydrates
Ripe grapes contain equal amounts of glucose and
fructose, while fructose predominates in overripe
or botrytised berries.
In addition L-arabinose (ca. 1 g/l), rhamnose (up
to ca. 400 mg/l), galactose (up to ca. 200 mg/l),
D-ribose (ca. 100 mg/l), D-xylose (ca. 100 mg/l)
and mannose (up to ca. 50 mg/l) are present.
Saccharose (ca. 10 g/l) is detectable only if the
saccharase is inhibited during pressing. Other
oligosaccharides present are: raffinose (up to ca.
200 mg/l), maltose (ca. 20 mg/l), melezitose (ca.
20.2.3.3.3 Nitrogen Compounds
Proteins, which include various enzymes, peptides
and amino acids, are present in low amounts
(cf. 18.1.2.1)
20.2.3.3.4 Lipids
The lipid content of must is about 0.01 g/l.
20.2.3.3.5 Phenolic Compounds
Tannins occur primarily in stems, skin and seeds.
In a carefully prepared white must, the tannin
content is no more than 0.2g/l. In contrast, red
wines contain high levels of tannin, 1–2.5g/l
or even higher. In white grapes, quercetin,
its 3-rhamnoside quercitrin and carotinoids
contribute to the color. The main part of the
color pigments of European red-wine vines are
free (unesterified) anthocyanidin-3-glucosides
with malvidin-3-glucoside (40–90% of the
anthocyans) as the dominating compound. Apart
from the 3-monoglucosides, anthocyanidin-
3,5-diglucosides also occur on crossing with
American cultivars (hybrids).
β-Glucosidases, which come from yeast, hydrolyze
the free anthocyanidin glucosides to