Food Chemistry

20.2 Wine 915

Table 20.14.Quality levels and natural minimum alco-
hol content of German wines

Quality level Minimum alcohol contenta

Zone Ab Zone Bb

Table wine 5. 06. 0
Country wine 5. 56. 5
Quality wine 7. 0 c 8. 0
Quality wine with vintage

• Cabinet 9. 5 d 10. 0


• “Spaetlese” 10. 011. 4


• “Auslese” 11. 113. 4


• “Beerenauslese” 15. 317. 5


• Ice wine 15. 317. 5


• “Trockenbeeren” 21. 521. 5

ain % vol.
bVine growing areas: Germany without Baden

(Zone A), Baden (Zone B).
cPartly 6.0.
dPartly 9.0.

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 corre-
sponding values for German wine are presented
in Table 20.14.
Since the density of the must is primarily depen-
dent 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 additionL-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.

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 is65–70% 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.

20.2.3.3.3 Nitrogen Compounds

Proteins, which include various enzymes, pep-

tides 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, hy-

drolyze the free anthocyanidin glucosides to