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New Ideas for Measuring Oxidation Andrew L. Waterhouse
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Collaborators Maurizio Ugliano Bruce Currie Stephane Vidal Jean-Baptist Dieval Olav Aagaard Mauri Anderson Alexander Chassy
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Wine Oxidation Reactions
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Managing Wine Oxidation Oxygen is consumed Quinone reversal to phenol Limit Fenton oxidation Quench H 2 O 2 Reactions of Fenton products Color development Measure Oxygen Consumed!
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Measure Oxygen Consumed in Bottle? Oxygen entering bottle At bottling From closure Oxygen transfer through closure Subtract residual oxygen Balance: consumed oxygen How can we measure oxygen entering bottle
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Oxygen Measurement in Bottles, etc Device emits blue flashes Dots in container luminesce with red light Rate of decay is related to [O 2 ]
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Measuring Oxygen Entering Bottle Model Bottle Diéval JB, Packag. Technol. Sci. 2011; 24: 375–385 Provides prediction for the same closures!
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Oxygen Consumption by Wine Add oxygen entering bottle Oxygen at bottling Oxygen from closure transmission (model bottle) Subtract current O 2 (Nomasense) Difference is Total Consumed Oxygen, TCO Oxygen that has been consumed by wine Apply to an experiment
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Interaction of Wine Prep, Closures Experiment on Chardonnay Chardonnay Wines Oak barrel vs SS barrel Lees aging vs no lees Four Closures Light Premium Premium, 4% O 2 Premium, N 2 Accelerated Aging Experiment High O 2 at bottling
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Measurements O 2 by Nomasense Carbonyls by DNPH Phenolics by HPLC SO 2 by Ripper others
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DO and HSO
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TCO Data
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Free SO 2 Data
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Sulfur Dioxide and Oxygen Theoretical Balanced Reaction 2 SO 2 + O 2 → 2 SO 3 Mass ratio, 4 SO 2 to O 2 So, with 4/1 ratio of consumption Balanced reaction Complete protection from oxidation Ratio below 4: oxidation of other components
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Antioxidant Reactions of SO 2
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Consumed Free SO 2 /TCO At End of Experiment
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Different Consumption Ratios Lees aged wine had higher Consumed SO 2 /TCO 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
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Relative Reaction Rates of Nucleophiles Nikolantonaki, JAFC, 60: 8484 (2012)
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Protection of SO 2 SO 2 : Fast rate of reaction with quinones 3-5 mg/L free SO 2 Thiols, 1 ug/L or less Rate 7x faster than 3MH Amount >1000x less Overall SO 2 rate ~ 10,000 times faster Phenolics, 70 mg/L total Rate 50,000x faster Overall 5,000 x advantage BUT: free SO 2 is not being depleted as expected
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Model Quinone SO 2 reaction
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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”
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Measurement of Free SO 2 Titration with I 2 Appearance of excess I 2 after SO 2 depleted
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Weak SO 2 Binding Agents Pyruvate Alpha-keto glutaric acid Galacturonic Acid Other aldehydes, ketones
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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
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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?
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Improved SO 2 Measurement Predictive of reactive SO 2 Quick measurement Avoids dilution or equilibration effect from titration or other treatment
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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 development- phenolics Protection by “free” SO 2 is not linear Interference by carbonyls? Free SO 2 measures need improvement
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Major Support Nomacorc American Vineyard Foundation
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