Reduction Redux The Good, the Bad and the Nutty. The closure issues. Presented by Adrian Coulter Senior Oenologist AWRI

Transcription

1 Reduction Redux The Good, the Bad and the Nutty The closure issues Presented by Adrian Coulter Senior Oenologist AWRI

2 1999 Semillon wine bottled using 14 different closures Range of color 28 months after bottling OD au OD au 14 different closures 14 different wines!

3 PCA map of 63 month aroma data (1999 Semillon wine) oxidised PC1 (60%) honey Ref Ref Ref 2 Ref 2 Ref 3 Ref Ref Ref 3 Ref 3 Ref 2 Ref 2 Ref 2 Ref 3 Ref 3 Ref PC2 (19%) toasty lime overall aroma citrus struck flint rubber Ref 2 TCA

4 Wine development is closely connected with oxidation reduction phenomena (redox reactions) depends on a whole series of factors relating to the wine s composition and storage conditions Post-bottling: depends on wine composition, storage conditions and the properties of the closure

5 Wine composition Dissolved oxygen Ascorbic acid SO 2 Phenolic compounds Metal ions Flavour compounds Oak phenolics Fermentation-derived compounds (thiols). Bottling Dissolved oxygen Oxygen in headspace Oxygen permeability of closures Filling height SO 2 Wine storage Permeability of closures (transfer of gases in and out of the bottle, closure type, storage position) Flavour scalping Temperature Time. Wine development oxidation/reduction, and consumer satisfaction

6 AWRI commercial closure trial bottled September 2002 (Auscap, tin liner) - four treatments at bottling Low filling height (48mm ullage, Free SO 2 38 mg/l) Low filling height + SO 2 (47mm ullage, Free SO 2 54 mg/l) High filling height (30mm ullage, Free SO 2 39 mg/l) High filling height + SO 2 (29mm ullage, Free SO 2 59 mg/l)

7 Relationship between free SO 2 and struck flint aroma score: 24 months storage Struck flint aroma score Low High Low Low Low High High High Low+SO 2 High+SO 2 High+SO 2 Low+SO 2 Low+SO 2 High+SO 2 High+SO 2 Low+SO Free SO 2 (mg/l)

8 Sulfur equilibrium in wine reduction oxidation methanethiol 1.5 μg/l CH 3 S-H hydrolysis acetylation dimethyl disulfide 10 μg/l CH 3 S SCH 3 methyl thioacetate 40 μg/l CH 3 C SCH 3 O

9 Relationship between free SO 2 and struck flint aroma score: 24 months storage (n=4) 2.5 Struck flint aroma score Low High High+SO 2 Low+SO Free SO 2 (mg/l)

10 Free SO 2 concentration and rubber aroma score: 63 months storage Mean score for Rubber Ref Ref 2 Ref 3 Ref Ref Ref 2 Ref Ref Ref 3 Ref 2 Ref 3 Ref 3 Ref Ref 3 Ref 2 Ref Free SO 2 (mg/l)

11 Free SO 2 concentration and struck flint aroma score: 63 months storage Mean score for Struck flint Ref Ref Ref 3 Ref Ref Ref Ref Ref Ref 3 Ref 3 Ref Ref 3 Ref 2 Ref 2 Ref Free SO 2 (mg/l) Ref 2

12 Development of reductive characters in wine after bottling Wines bottled with low oxygen permeation closures are more likely to develop reductive character in bottle, if those wines have a propensity to become reductive

13 Panel mean scores for the attribute reduced 0.5 Attribute mean score Semillon Sauvignon Blanc Sauvignon Blanc Chardonnay Bottle number

14 Panel mean scores for the attribute TCA 7.0 Attribute mean score Semillon Sauvignon Blanc Sauvignon Blanc Chardonnay Bottle number

15 Panel mean scores for the attribute oxidised 0.4 Attribute mean score Semillon Sauvignon Blanc Sauvignon Blanc Chardonnay Bottle number

16 Panel mean scores for a 2003 Chardonnay wine sealed with natural cork closures 5 Attribute mean score Attributes Oxidized TCA Reduced ng/l of TCA Bottle number

17 Panel mean scores for a 2004 Shiraz wine sealed with screw cap and cork closures 3 Attribute mean score 2 1 Attributes TCA Oxidized Reduced Screw cap sealed bottles Cork sealed bott 12

18 Impact of closure type and ascorbic acid addition on oxidized score after 3 years 7 Chardonnay Riesling Oxidised aroma score LSD LSD 0 Cork 1 Cork 2 Synthetic Screw cap Cork 1 Cork 2 Synthetic Ascorbic acid at bottling: added not added Screw cap Skouroumounis et al (2005) Aust. J. Grape Wine Res, 11, &

19 Impact of closure type and storage position on a Chardonnay wine aroma after 3 years 5 4 oxidized LSD flint/rubber LSD Aroma score Cork 1 Cork 2 Syn. Screw cap Cork 1 Cork 2 Storage position: upright inverted Syn. Screw cap Skouroumounis et al (2005) Aust. J. Grape Wine Res, 11, &

20 Commercial closure trial: 2002 Semillon different closures & times post-bottling Attributes Oxidized Reduced Screw cap Ref 2 Ref 3 ProCork Months since bottling What Is Procork? AWRI Commercial Closure Trail Reports, 12, 18, 24 and 36 months. [ m.au/whatisprocork/ind ex.html]

21 2004 Chardonnay wine sealed with membrane corks: 24 months post-bottling Attributes Oxidized Reduced Bottle number Bottles stored in an upright position for 18 months post-bottling

22 Impact of closure type, including glass ampoules, on wine aroma after 4 years Riesling Chardonnay 3 oxidized LSD flint/rubber LSD 3 oxidized LSD flint/rubber LSD Aroma score 2 1 Aroma score Cork 2 Screw cap Glass ampoule Cork 2 Screw cap Glass ampoule 0 Cork 2 Screw cap Glass ampoule Cork 2 Screw cap Glass ampoule Skouroumounis et al (2005) Aust. J. Grape Wine Res, 11, &

23 Wines bottled with closures with low oxygen transmission rates (OTRs) are more likely to develop reductive character in bottle, if those wines have a propensity to become reductive It is therefore incorrect to say that low OTR closures CAUSE reductive character

24 Oxygen at bottling is consumed within weeks Reductive characters, probably thiols, are formed over months or years Oxygen to oxidize the thiols is that permeating through the closure Increasing the headspace volume is oxygen at the wrong time

25 Fermentation management Yeast strain Problem or stressed fermentations are more likely to contain higher concentrations of thiols and their precursors. These wines will cause greater problems with post-bottling reduction

26 Fermentation management Better yeast preparation, particularly during rehydration, and aeration of the culture Avoid temperature shock Add air and nitrogen one third of the way through fermentation

27 After fermentation Know what the sulfur compounds are before aerating wine after fermentation - copper cadmium test Add copper if necessary, but be aware that copper can impact on longevity as it is a catalyst for oxidation

28 Acknowledgements Peter Godden, Dr Elizabeth Waters, Dr George Skouroumounis, Dr Alan Pollnitz, Tracey Siebert, Mariola Kwiatkowski The AWRI Industry Services Team: Con Simos, Geoff Cowey, Matthew Holdstock, Emma Kennedy and Sarah Ballantine All the AWRI staff who have been involved with the closure trials, especially the Analytical Service, and members of the sensory panel All the other individuals and companies who have assisted with the studies This work was financially supported by Australia's grapegrowers and winemakers through their investment body the Grape and Wine Research and Development Corporation, with matching funds from the Australian Government