Wine Chemistry and Biochemistry

8B Polyfunctional Thiol Compound 287

H 3 CCCH 2 C CH 3

CH 3 O

S

CH 2 CH COOH

NH 2

H 3 CCCH 2 CH

CH 3

CH 3

OH

H 3 CCH 2 CH 2 CH CH 2 CH 2 OH

S

CH 2 CH COOH

NH 2

S

CH 2 CH COOH

NH 2

S-4-(4-methylpentan-2-ol)-L-cysteine

S-3-(hexan-1-ol)-L-cysteine

S-4-(4-methylpentan-2-one)-L-cysteine

4MSP 4MSPOH

3SH

Fig. 8B.6Structure of three aroma precursors of sauvignon:S-cyteine conjugates

0 20 40 60 80 100

%

P-3SH

P-4MSPOH

P-4MSP

Skin

Juice

Seeds

Fig. 8B.7Distribution of cysteinylated precursors in a ripe berry of sauvignon

viticulture conditions on Sauvignon blanc aromatic maturity (Peyrot des Gachons

et al. 2002a; Murat et al. 2001b).

More recently, a new method was developed to determine the diastereoisomeric

distribution of P-3SH in grape juice. P-3SH assays in Bordeaux white grape juice

affected byBotrytis cinereashowed an unusually increased proportion of theRS

form of the precursor (approximatelyRR:RS=30:70) as compared to a diastereoiso-

mer ratio (in the vicinity of 50:50) in healthy grape juice (Thibon et al. 2007, 2008a)

Sauvignon aroma is enhanced during fermentation (Fig. 8B.9) because of the

conversion of cysteinylated aroma precursors. 3SH is released during the fermen-

tation of a model medium added withS-3-(hexan-1-ol)-L-cysteine. When fermen-

tation is inhibited by pimaricin, the development of aroma and the degradation of