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Tomás Román Villegas 1, Roberto Larcher 1, Mario Malacarne 1, Loris Tonidandel 1, Daniele Zatelli 1 and Giorgio Nicolini 1* 1 FEM Fondazione Edmund Mach, via E. Mach 1, 38010 San Michele all’Adige, TN, Italy
*Email:giorgio.nicolini@fmach.it
INTRODUCTION
INTRODUCTION
So-called varietal thiol precursors 3-S-cysteinyl- and 3-S-glutathionyl-hexan-1-ol (Cys-3MH and GSH-3MH, respectively) were recently found for the first time in some commercial tannins, mainly derived from grape skin [1-2]. The maximum measured concentrations are rather high - about 300 and 200 mg/kg powder, respectively - thus suggesting several new potential applications for grape tannin. The ability of some commercial samples of this additive or clarifying agent to increase the wine free thiols - responsible for tropical and grapefruit-like notes - has already been observed on the laboratory scale [3]. Here, we give evidence of the possibility to enhance these such interesting sensory notes, and hence wine appreciation, using thiol precursors-rich tannins in semi-industrial Sauvignon Blanc and Aromatic Traminer vinifications.
MATERIALS
MATERIALS
&
&
METHODS
METHODS
The following effects were investigated:
- the type of the grape tannin supplemented (High thiol precursors vs Low precursors vs unspiked Control) - the yeast strain used (VIN13 vs VL3)
- the timing of tannin supplementation (fermentation onset vs fermentation completion)
Effect of the type of tannin and yeast strain.
Sauvignon Blanc (SB; n=3) and Aromatic Traminer (TR; n=3) very clear juices were spiked with a grape tannin rich in precursors (H; Cys-3MH, 125 mg/kg; GSH-3MH, 162 mg/kg) and fermented. These were compared with the same juices spiked with a grape tannin poor in precursors (L; Cys-3MH, 0.1 mg/kg; GSH-3MH, 0.3 mg/kg) and with unspiked control juices (C). Neither H nor L contained 4MMP precursors. Taking account of the role of fermentation temperature on free thiol derivatives’ liberation/formation [4], fermentations were carried out at 18-20°C using 2 yeast strains with lyase activity on thiol precursors. Argon blanketing was used to prevent oxidation (Figure 1).
Effect of the timing of the tannin supplementation
When the 3 Sauvignon Blanc control wines produced with the strain VIN13 had about 3 g/L of residual sugar, an aliquot was separated and supplemented with the precursor rich grape tannin (H; 500 mg/L). At the end of the fermentation spiked wines were processed as in Figure 1.
Analysis
Thiol precursors were analysed according to [1]. The orthonasal olfaction of wine – to avoid afteraromatic interferences [5-6] – was performed by 2 panels: A, made up of 17 judges expert in the evaluation of 3- mercaptohexanol and its acetate; B, 18 expert winemakers of Traminer. In Traminer, only the wines produced with VIN13 were subject to sensory analysis. Paired tests were evaluated according to [7]. STATISTICA v. 8.0 (StatSoft Inc.) was used in the other cases.
RESULTS
RESULTS
As expected, only the addition of the precursors’ rich H tannin increased the thiol precursors in juice. The mean value of the control juices was lower in TR than in SB, particularly Cys-3MH (Figure 2).
CONCLUSION
CONCLUSION
• Only the addition of a grape tannin rich in thiol precursors significantly increases the perception of thiol-related aroma nuances, reasonably as a consequence of the release of 3-mercaptohexanol and subsequent formation of its acetate.
•This “additive" aroma does not prejudice the typicality of the Aromatic Traminer wine aroma. •When applied near the completion of fermentation, the treatment is ineffective.
• No or very limited differences were perceived between VIN13 and VL3 as regards thiol-related aroma intensity.
THE USE OF COMMERCIAL GRAPE TANNINS CAN INCREASE THE
3-MERCAPTOHEXANOL PRECURSORS IN JUICE AND
AFFECT THE TROPICAL FRUITY CHARACTERISTICS OF WINE
Cavit s.c. is acknowledged for economic support Poster reference number 12012
Figure 1. Experimental protocol applied to 3 Sauvignon B. and 3 Aromatic Traminer grapes.
Figure 2. Content of thiol precursors in juice (mean ± st.dev.; n=3 juices).
DESTEMMING, CRUSHING
COLD SETTLING (10°C, 36 h), DECANTING
CONTROL (high precursors)TANNIN H (500 mg/L) SO2 (50 mg/L), PECTIC ENZYME ( 0.015 mL/L) TANNIN L (low precursors) (500 mg/L) VIN13 (300 mg/L) VL3 (300 mg/L) VIN13 (300 mg/L) VL3 (300 mg/L) VIN13 (300 mg/L) VL3 (300 mg/L) FERMENTATION (18-20°C),SO2 (80 mg/L), ARGON BLANKETING COLD STABILIZATION (0°C, 15 gg),
DECANTING UNDER ARGON BOTTLING & SENSORY EVALUATION
0 20 40 60 80 100 120 140 160 180 C L H C L H µg /L GSH-3MH Cys-3MH
SAUVIGNON BLANC AROMATIC TRAMINER
variety panelgrape
lot VIN13 VL3 sign. VIN13 VL3 sign.
1 8 9 n.s. 2 9 8 n.s. 3 9 8 n.s. 1 13 5 0.05 2 10 8 n.s. 3 7 11 n.s. n.s. TR 30 24 n.s. A (n = 17) B (n= 1 8) SB 26 25 0 1 2 3 4 5 6 7 8 9 C LH CLH CLH CLH CLH C LH ar bitr a ry un its (0 -1 0) VIN13 VL3 b b a bb a b aa bba b ba a aa
SAUVIGNON B - intensity of tropical and grapefruit-like notes
0 1 2 3 4 5 6 7 8 C L VIN13 H C L VL3 H ar b itra ry un its (0 -1 0) b b b b a a 0 1 2 3 4 5 6 7 8 9 C L H C L H ar b itrar y units ( 0 - 10)
grapefruit-like aroma typicality, overall appreciation
b b a b b a AROMATIC TRAMINER 0 1 2 3 4 5 6 7 CL H C L H CL H CL H C L H CL H a rbi tr ary uni ts (0 - 10)
grapefruit-like aroma typicality, overall appreciation
b b b b b b b b b a a a a a a ab ab ab
Effect of the yeast Effect of the yeast
No differences were found as regards the thiol- related aroma intensity
Comparison between the supplementation times Comparison between the supplementation times Thiol-related aroma intensity is higher with early tannin supplementation. Supplementation near the completion of fermentation is ineffective, confirming the early fermentative formation of the
free varietal thiols [8](Subileau et al. 2008).
SB grape lot; VIN13 @ fe rm e n ta ti o n on se t near fe rm e n ta ti o n co m p le ti o n sign. @ fe rm e n ta ti o n on se t near fe rm e n ta ti o n co m p le ti o n sign. 1 16 1 0.01 2 12 5 n.s. 3 12 5 n.s. 0.001 40 11 (panel A) 5) C. Starkenmann, B. Le Calvé, Y. Niclass, I. Cayeux, S. Beccucci, M. Troccaz, J. Agric. Food Chem.
56, 9575–9580 (2008)
6) C. Starkenmann, Y. Niclass, J. Agric. Food Chem. 59, 3358–3365 (2011) 7) E.B. Roessler, R.M. Pangborn, J.L. Sidel, H. Stone, J. Food Sci. 43, 940-943, 947 (1978) 8) M. Subileau, J.-M. Salmon, R. Schneider, E. Degryse, Enoforum 2008 Innovation et Performance,
Arezzo (I), poster n. 4, 58-59 (2008)
REFERENCES
REFERENCES Aroma intensity in SB (panel A):
H tannin > L tannin with both strains. No differences between L and C
In TR (panel B; VIN13):
H tannin > L tannin L tannin = C
H tannin enhances tipicality & wine
