Wine Chemistry and Biochemistry

256 R. Baumes

(berry set) until v ́eraison, then it favors their degradation into C13-norisoprenoidic

compounds, from v ́eraison to maturity (Bureau 1998), when chlorophyllic photo-

synthetic pigments disappear (Hardie et al. 1996). This degradation of carotenoids in

grape berry involves a carotenoid dioxygenase, VvCCD1 (Vitis viniferaCarotenoid

Cleavage Dioxygenase), cleaving the 9,10- and 9′,10′-double bonds of carotenoids

to release C13-norisoprenoidic carbonyl compounds, possessing the same oxidised

backbone as their carotenoidic parents (Fig. 8A.4) (Mathieu et al. 2005). These

primary products of cleavage are then transformed by oxidases and reductases to

C13-norisoprenoidic compounds at different oxidation degrees, and finally glycosy-

lated by grape glycosyltransferases (Ford and Hoj 1988; Wirth et al. 2003; Mathieu

et al. 2005). The regiospecificity of the enzymatic cleavage of carotenoids in grape

explains the predominance of the glycosidic norisoprenoids with 13 carbon atoms

identified in this fruit, but their total contents are approximately 10 times lower than

those of carotenoids (Baumes et al. 2002; Razungles et al. 1988).

However, in grape, VvCCD1 would not degrade carotenes into ionones, which

would explain the absence in this fruit of monooxygenated C13-norisoprenoids ,

whereas -carotene is a major carotenoid in grape (Mathieu et al. 2005). In addition,

in contrast to other C13-norisoprenoidic precursors of odorants in wine, e.g. -

damascenone or 1,1,6-trimethyl-1,2-dihydronaphtalene (TDN), no glycosidic pre-

cursor of -ionone was identified in grape or wine. Nevertheless, -ionone is a con-

stituent of wine, occurring in levels that do not exceed 1 g/L in wine, but higher

than those found in must from the same grapes (Kotseridis et al. 1998, 1999b).

Thus, -ionone would arise from the non enzymatic degradation of -carotene
during winemaking; it would be the same for -ionone and -cyclocitral, other

norisoprenoidic odorants identified in Melon B. grape (Kotseridis et al. 1998;

Schneider 2001; Silva Ferreira and Guedes de Pinho 2004). These carotenoid

Linear chain of 4 isoprenic units

2,2,6-Trimethyl

CyclohexylMethylene

at different

Oxidation levels

(2 isoprenic units)

Linear chain of 4 isoprenic units

2,2,6-Trimethyl

CyclohexylMethylene

at different

Oxidation levels

(2 isoprenic units)

NeoxanthineNeoxanthine

C C

C

CH 3 CH 3

H 3 C CH (^3) CH 3 CH 3
HO CH 3
O
H
C
H 3 C CH 3
HO
CH 3
OH
9'
9
10'
10
Fig. 8A.4Grape carotenoid general structure, neoxanthine and the chemical bonds cleaved byVitis
viniferaCarotenoid Cleavage Dioxygenase to biosynthesize the corresponding primary products of
cleavage (C13 norisoprenoids)