5/13/16. Oxygen Depletion. Wine Oxidation Reactions. Consumed SO2 Versus Consumed O2 in Bottle Aging

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1 5/13/16 Wine Flavor 101C: Managing Oxygen for Wine Composition and Stability Consumed Versus Consumed O2 in Bottle Aging Annegret Cantu Professor A.L. Waterhouse Oxygen Depletion Wine has an inherent ability to consume oxygen Whites ~ 10 air saturations; more, loss of varietal character Reds ~ 30 air saturations; 10 would benefit By comparing and O2 consumed in wine it is possible to observe wine s protection power against oxidation New tool for studying wine oxidation chemistry Wine Oxidation Reactions Y Fe+2 O2 H+ Fe+3 RCH2OH RCHO (Hydroperoxyl radical) (Hydroxyl radical) (Peroxyl radical) Fe+3 Fe+2 (Semiquinone radical) (Hydrogen peroxide) X (Quinone) 1

2 Managing Wine Oxidation Oxygen is consumed Quinone reversal to phenol Limit Fenton oxidation Quench H Reaction of Fenton products Color development Measure Oxygen Consumed! Measure Oxygen Consumed in the Bottle? Measure Oxygen Consumed in the Bottle? Oxygen entering bottle At bottling From Closure Oxygen Transfer Rate (OTR) Through Closure Subtract residual oxygen Balance = consumed oxygen How can we measure oxygen entering bottle? 2

3 Measuring Oxygen Entering Bottle Diéval JB, Packag. Technol. Sci. 2011; 24: Provides prediction for the same closure! Department A of Viticulture and Enology Oxygen Consumption by Wine Add oxygen entering the bottle Oxygen at bottling Oxygen from closure Subtract current O 2/ (NomaSense) Difference in Total Consumed Oxygen, TCO Oxygen that has been consumed by wine Experimental Design, Closure Experiment on Chardonnay Chardonnay wines Oak barrel vs stainless steel (SS) barrel Lees aging vs no lees Four Closures Light Premium Lees Premium, 4% O 2 Premium, N 2 Accelerated Aging Experiment High O bottling SS, Lees Container Barrel, Lees SS, no Lees Barrel, no Lees 3

4 Experimental Design Measurements O 2 by Nomasense Carbonyls by DNPH Phenolics by HPLC SO 2 by Ripper Others Dissolved Oxygen, DO and Headspace Oxygen, HSO Chardonnay wine in barrel with no lees C1 DO C2 DO C2 4% DO C2 N2 DO C1 HSO C1 HSO C1 4% HSO C1 N2 HSO

5 Total Consumed Oxygen Data (TCO) 07 Chard Ba no lees TCO (ppm) Light Prem Prem4% PremN Days Free SO 2 Data 07 Chardonnay Ba no Lees F (ppm) Light Prem Prem 4% Prem N Days Sulfur Dioxide and Oxygen Theoretical Balanced Reaction 2 SO 2 + O 2 2 SO 3 Mass ratio, 4 SO 2 to O 2 So, if 4/1 ratio of consumption (mg/l) Balanced reaction Complete protection from oxidation Ratio below 4: oxidation of other components 5

6 Antioxidant Reactions of SO 2 Fe +2 Fe +3 RCHO RCH2OH O2 H + (Hydroperoxyl radical) (Peroxyl radical) Fe +3 Fe +2 (Semiquinone radical) (Hydrogen peroxide) H2O (Quinone) Consumed Free SO 2 / TCO Consumed Free SO 2 / TCO Lees aged wine had higher consumed SO 2 / TCO than others How can we explain different ratios? Lees aging increases ratio WM s report that lees aging is protective Lees aged wines had less pyruvic acid 6

7 Model Quinone SO 2 reaction Effect of Pyruvic Acid Decreases the ability of SO 2 to reduce quinone Compromises the antioxidant effect of SO 2 Need to understand which wine components are affecting these reactions Weak binders I - I2 k, fast no reaction Weak SO 2 Binding Agents Pyruvate Alpha-keto glutaric acid Galacturonic Acid Other aldehydes, ketones 7

8 Barrel Aging on Lees Lower level of pyruvic acid! Yeast lees or bacteria seem to metabolize aldehydes and ketones, reducing them to the alcohol form Thus, the free SO 2 as currently measured, is more available for protective reactions So, during oxidation, the consumed SO 2 / TCO ratio is higher Application of SO 2 /TCO Ratio May be predictive of protection by SO 2 Measurement takes time At least two time points needed Need time to consume both oxygen and SO 2 Could a titration of SO 2 versus SO 2 /TCO ratio show what level of SO 2 could be protective? Improvement of SO 2 Measurements Predictive of reactive SO 2 Quick measurement Avoids dilution or equilibration effect from titration or other treatment k, fast SO4-2 no reaction 8

9 Summary TCO in bottle is a key new measurement Based on consistent closures Comparison of TCO vs SO 2 consumed appears to be useful Ratio of 4 indicates no oxidation products Ratio below 2 leads to significant oxidation Value below 4 needed for developmentphenolics Protection by free SO 2 is not linear Interference by carbonyls? Free SO 2 measures need improvement Collaborators Maurizio Ugliano Bruce Currie Stéphane Vidal Jean-Baptiste Diéval Olav Aagaard Mauri Anderson Alexander Chassy The study was supported by Nomacorc 9