Wine Chemistry and Biochemistry

9C Non-flavonoid Phenolic Compounds 515

Phenols R 1 R 2 R 3 MW

CH 3

C 2 H 3

C 3 H 7

C 3 H 5

154

HHC 2 5 H 122

H C 2 H 3 H 120

OCH 3 OH H 124

OCH 3 H 122

OCH 3 C 2 H 5 H 136

OCH 3 H 134

OCH 3 H 150

OCH 3 H 148

OCH 3 HOCH 3

Ethyl phenol

Vinyl phenol

Guaiacol

Methyl guaiacol

Ethyl guaiacol

Vinyl guaiacol

Propyl guaiacol

Allyl guaiacol

Syringol

Methyl syringol OCH 3 CH 3 OCH 3 152

OH

R 3 R 1

R 2

Fig. 9C.4Structures of volatile phenols in wine

More potent yeasts responsible for spoilages of wines with volatile phenols are of

Brettanomyces/Dekkerratype that can produce the vinyl phenols and ethyl phenols

of hydroxyl cinnamic acids. Rib ́ereau-Gayon et al. (2000) give an overview on this

topic. Another source of volatile phenols is the oak wood of barrel and oak chips.

These phenols are characterized by smoked and toasted aromas. Important volatile

phenols in wine are depicted in Fig. 9C.4.

9C.3 Stilbenes

Stilbenes are a subclass of phenolic compounds naturally occurring in various fami-

lies of plants, but grapes and wine are considered the most important dietary sources

of these substances (Guebailia et al. 2006). Stilbenes can be biosynthesized by

grapevines as a defence response to stress, such as microbial infection and UV irra-

diation, and they are transferred during the winemaking process into the must and

wine. Due to their antioxidative, anticarcinogenic and antimutagenic potency, stil-

benes are considered to play a central role in the human diet (Buiarelli et al. 2007).