Food Chemistry

20.1 Beer 905

Fig. 20.3.Terminology for the description of odor and taste notes of beer (American Society of Brewing Chemists,
according toMeilgaard, 1982)

Nine of the terms given in Fig. 20.3 describe the
most important odor and taste characteristics of
a good beer (Table 20.8). They are also suitable
for the differentiation of different types of beer
(Table 20.8).
Foaming is an important criterion of the taste of
beer. A distinction is made between foam vol-
ume (produced by the content of carbon diox-
ide), foam density, and especially foam stabil-
ity (caused by protein degradation products, bit-
ter hop compounds, and pentosans). Lower fatty
acids that are present in beer bouquet act as de-
foamers.
Beer defects detract from the odor and taste and
are caused by improper production and storage.
An example of a taste defect is the harsh, hard,

bitter taste produced by the oxidation of polyphe-

nols and some hop constituents. A flat taste, as

already mentioned, comes from a low content of

carbon dioxide. Diacetyl and ethanal in concen-

trations greater than 0.13 mg/l and 25 mg/lre-

spectively, produce a taste defect. Acceleration

of fermentation caused, e. g., by intensive stir-

ring of the wort, raises the content of diacetyl

and higher alcohols in the beer and lowers the

content of esters and acids. On the whole, the

aroma is negatively influenced. Higher concen-

trations of ethanal can arise, e. g., at higher fer-

mentation temperatures and higher yeast concen-

trations.

Beer is very sensitive to light and oxidation. The

“light” taste is due to the formation of 3-methyl-