288 D. Dubourdieu and T. Tominaga
0
200
400
600
800
1000
0h 3h 6h 14h 19h
P-4MSP and P-4MSPOH
0
20000
40000
60000
80000
100000
120000
P-3SH
P-4MSP
P-4MPSOH
P-3SH
ng eq. /L ng eq. /L
Fig. 8B.8Influence of skin contact on the cysteinylated precursors of the must (Peyrot des
Gachons et al. 2002a)
0
25
50
75
0123456
0
500
1000
1500
ng/L released
days
4MS
POH
4MS
P
3SH
Fig. 8B.9Sauvignon blanc aroma revelation during alcoholic fermentation in practical conditions:
yeast strain VL3c (Tominaga et al. 1998c)
the precursor are very limited (Fig. 8B.10). The molar concentrations of 4-MSP
4-MSPOH, and 3-SH formed in Sauvignon blanc must (or a model medium supple-
mented with precursors) during alcoholic fermentation only account for less than
10% of the precursors degraded (Fig. 8B.11).
To be transformed in aroma, the precursor must enter into the yeast, then be
cleaved by – elimination of the cysteinylated precursor and finally excreted in
the medium where it is more or less stableaccording its reactivity with other com-
pounds. Obviously, the yield of this transformation can be influenced by several