Recent Developments in Wine xidation Chemistry Andrew L. Waterhouse Cornell University, September 13, 2011
xidation Two Stages H 2 + H Step 1 Fenton + + H22 Acetaldehyde Step 2 ther Prods
Polyphenols are Pro-oxidants Generation of quinone and hydrogen peroxide from dioxygen Fe +2 2 H + H + H H + H H
xygen Pathway in Wine RC= 2 Fe +2 Fe +3 1 H H + H H 2 + RC= (Hydroperoxyl radical) H + H H RCH 5 H 2 R H + Fe +3 C H RCHH (Hydroxyl radical) H + Fe +3 4 Fe +2 H H + H 2 (Semiquinone radical) (Hydrogen peroxide) 3 (Quinone)
Effect of 4-MeC on xidation Danilewicz, AJEV 59: 128 (08)
xidative Reactions in Wine Formation of quinones from catechols React with thiols Reversal by S 2 Fenton oxidation of alcohols, acids Formation of aldehydes, ketones Color and aroma development Loss of all other components
Quinone Alternative Reactions H H? H H H Phloroglucinol Ascorbate RSH H H H Phenolic Coupling (polymerization) H S2 (Quinone) AA's, Strecker Degradation S Mercaptan Trapping R H H Aldehydes?
Quinone Reaction with Mercaptans Loss of highly aromatic mercaptans Many negative components Hydrogen sulfide Ethyl mercaptan and others Some positive components 3-mercaptohexanol Rapid reaction with oxidation Trace components
Catechin + 3-Mercaptohexanol H H H H H H + H SH H H H S Nikolantonaki, ACA 660: 102 (10) Blanchard, AJEV 55:115 (04)
Reaction with ther Mercaptans Quinone can react with H 2 S, other mercaptans Reaction to remove reduced aroma Very fast H H H H H + H 2 S H H H SH
Quinone + Gluthathione Formation of GRP Protective of 3-MH? Coutaric H R H R PP, 2 Cafftaric acid Quinone Brown Pigments H G-S R H n NH 2 HC-CH 2 -NH-C-CH-NH-C-CH 2 -CH 2 -CH-CH CH 2 H CH HC CH CH C H C H S H H 2-S-Glutation caftaric acid GRP Quinone
Aromatic Aldehydes from Quinones? Possible Strecker Degradation Branched Aldehydes Methylpropanal, 2-methylbutanal, 3- methylbutanal Methional Phenylacetaldehyde Culler at al, JAFC 55:876 (2007)
Catechin dimer in model juice Poupard, J Chrom A, 1179: 161 (08)
Quinone Reactions Reduction by S 2 Thiol addition 1 vs 2 vs 3 Ascorbate reduction Amino acid, Strecker reaction Phloroglucinol addition
Second Stage of xidation Reaction of Hydrogen Peroxide with Iron Fenton reaction Formation of Aldehydes, ketones
Fenton Reaction Extremely reactive hydroxyl radical xidizes the first molecule it encounters xidation products are determined by concentration of wine components Antioxidants cannot protect against this oxidation Prevention by S 2 to trap peroxide
Wine Minor Components Red Wine Composition, Minor Components Acetaldehyde Volatile Acidity Glycerol Sugar Higher Alcohols Phenols Sorbitol & Mannitol Sulfites Minerals * Esters Amino acids Acid
Fenton Products Ethanol yields acetaldehyde Lactic and Malic acids yield pyruvate Glycerol yields glyceraldehyde Many other aldehydes, ketones
Ethanol to Acetaldehyde Ethanol C H 3 C H H 2 H H 3 C C H H Hydroxyl radical Acetaldehyde C H 3 C H
Ethoxyl Radicals (A) Fenton system (B) CabS (44 h) (C) Simulation 3330 3340 3350 3360 3370 3380 3390 3400 Magnetic field (Gauss) Elias, J. Agric. Food Chem., 57: (2009).
xidation of Wine Acids (Alcohols) to Carbonyls Pyruvic bserved in wine Reacts with anthocyanins to make wine pigments H CH 3 H Lactic Acid (or Malic) H 2 2 Fe +2 H CH 3 Pyruvic Acid Glyoxylic bserved in wine Condenses with flavan-3-ols H H H H Tartaric Acid H 2 2 Fe +2 H H H Hydroxymalonic H CH Glyoxylic Acid
Aldehyde Pigment Reactions D-ring formation by acetaldehyde and pyruvate H H + Glu R1 H R2 or H H H R + Glu R1 H R2 R = H, H
Aldehyde Coupling of Flavonoids Tannin, anthocyanin coupling Es-Safi, J. Agric. Food Chem. 48: 4233 (2000). Es-Safi, J. Agric. Food Chem. 47: 2096 (1999).
Important xidation Aldehydes Branched Aldehydes Methylpropanal, 2-methylbutanal, 3- methylbutanal Methional Phenylacetaldehyde Cullere at al, JAFC 55:876 (2007)
Formation of Branched Aldehydes Fenton oxidation of alcohols H H H CH CH CH S H S CH
Sotolon Formed from sugars? Ferreira, JAFC 51:4356 (03) Descriptors, 8 ug/l threshold Nutty, Curry, Dried fig, Rancio Important in Vin Jaunes (Jura), port, Vins doux Naturel (fortified) Defect in fresh whites
Impact of Fenton Products Color development Production of S 2 stable wine pigments from grape anthocyanins Aroma impact. Aldehydes and ketones captured by S 2 binding, until free S 2 depleted oxidized character
Fenton Inhibition in Model Wine Inhibition of Acetaldehyde 1.1 Acetaldehyde (Norm) 0.9 0.7 0.5 Gislason, J. Agric. Food Chem., 59: 6221 (2011).
Fenton Inhibition by Cinnamates Acetaldehyde (Norm) 1.1 0.9 0.7 R 1 H R R 2 1 R 2 (Hydro)Cinnamic Acid: R 1 /R 2 = H (Hydro)Caffeic Acid: R 1 /R 2 =H H 0.5 NP HCinn HCaff Cinn Caff
xidation Product of Cinnamates Two Products Coumaric, Caffeic or Ferulic
Ferulic Products H H H Me H Et H Me H +, MeH H Me H +, EtH H Me
Mechanism of Ethoxyl Trapping H C H H Me C H H Me H Fe(III) H Fe(II) H C 2, H + C + H H Me H Me H
Cinnamates Fenton Antioxidants? Cinnamates react with ethanol radical Decrease acetaldehyde production Reaction may release dihydroxybenzaldehydes (aroma?)
Polymers Anthocyanins Wine Pigments quenched 2 Fe +2 Fe +3 H + H H H H H H + RC= (Hydroperoxyl radical) H H Phenolic Coupling (polymerization) + RCHH (Semiquinone radical) Resorcyl H H H (Quinone) Aldehydes 2 H R C HH + (Hydroxyl radical) RSH AA's, Strecker Degradation H + H H cinnamates RCH2H Fe +3 Fe +2 (Hydrogen peroxide) H + H S H 2 R S2 Sulfide Trapping H H2 Fe +2 recycling by phenolic reduction H
Acknowledgements American Vineyard Foundation CCGPREV Nomacorc SA Collaborators: University of Copenhagen Nick Gislason, Screaming Eagle
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