Wine Chemistry and Biochemistry

4 Enzymes in Winemaking 111

R’

R

a-L-Arabinofuranosyl-

b-D-Apiofuranosyl-

a-L-Rhamnopyranosyl-

b-D-Glucopyranoside

Aliphatics

Monoterpenes

Terpene diols

C 13 norisoprenoids

Benzenoids

COH

O

HOH 2 C

OH

OH

O

O

OH

H 2

O

OH

O

O

OH

CH 3

OH

OH

HO

O

O

OH

CH 2

HO OH

R'

R

Fig. 4.3Chemical structure of the various possible glycosides identified in grapes

grapes (Cordonnier and Bayonove 1974; Winterhalter et al. 1990, 1991; Winterhalter

1991; Sefton et al., 1993, 1994; Sefton 1998; Wirth et al. 2002). For this reason, it

is generally accepted that hydrolysis of glycosides during winemaking is one of

the main factors determining the formation of wine aroma characteristics (Abbott

et al. 1991; Francis et al 1992, 1999). The liberation of glycosidically-bound aroma

compounds can be achieved either via an acid-catalyzed process or by the action of

glycosidase enzymes. Acid hydrolysis is however fairly slow under typical wine-

making conditions, and is mainly regarded as a pathway for the formation of wine

aging bouquet (Sefton 1998). Conversely, the action of glycosidase enzymes can

rapidly hydrolyze the aroma precursors and release the bound volatile compound

(G ̈unata et al. 1993). This approach has therefore attracted considerable attention for

its possible application as a tool to modulate wine aroma and enhance the expression

of specific sensory characteristics.