Effect of xidation on Wine Composition Andrew L. Waterhouse University of British Columbia, Kelowna Mar 25, 2011
xygen Reduction Cascade +e - +e - 2.- 2 Superoxide 2 2- Peroxide +e - +e - Hydroxyl radical At wine ph +H + +H + +H + H. 2 H 2 2 Hydroperoxyl Hydrogen peroxide radical 2 Water
xidative Changes in Wine Formation of quinones from catechols React with thiols, amino acids Formation of aldehydes Fenton oxidation of alcohols Formation of aldehydes Loss of all other components
Polymers Wine Pigments Fe +2 Fe +3 2 H + H + RC= (Hydroperoxyl radical) Anthocyanins + RCH H 2 H (Semiquinone radical) R C H + (Hydroxyl radical) H + RCH 2 Fe +3 Fe +2 + H (Hydrogen peroxide) H 2 Fe +2 recycling by phenolic reduction H Phenolic Coupling (polymerization) Resorcyl (Quinone) Aldehydes RSH AA's, Strecker Degradation S 2 H 2 S R Sulfide Trapping
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
Quinone + Gluthathione Formation of GRP Coutaric R R PP, 2 Cafftaric acid Quinone Brown Pigments G-S H R n NH 2 HC-CH 2 -NH-C-CH-NH-C-CH 2 -CH 2 -CH-C CH 2 H C HC CH C C H C H S 2-S-Glutation caftaric acid GRP Quinone
Reaction with ther Mercaptans Quinone can react with H 2 S, other mercaptans Reaction to remove reduced aroma H + H 2 S H SH
Catechin + 3MH (mercaptohexanol) H + H SH H S
Protected Mercaptans Preserved 3MH percursors, i.e. 3MH-S- Cys/Glutathione are not lost to oxidation Roland, A JAFC 58: 4406 (2010)
Strecker Degradation AA s react with diketones, release aldehydes
Possible Strecker Source of Branched Aldehydes Derived from AA s either directly or via alcohols and yeast conversion NH 2 NH 2 NH 2 CH CH CH
Aromatic Aldehydes from Quinones Branched Aldehydes Methylpropanal, 2-methylbutanal, 3- methylbutanal Methional Phenylacetaldehyde Culler at al, JAFC 55:876 (2007)
Methional Cooked vegetable, pungent aroma bscures positive aromas Formed by Strecker degradation of amino acids or oxidation of alcohol S S NH 2 CH
Phenylacetaldehyde ld wood reduction-descriptor bscures positive aromas Formed by Strecker degradation of phenylalanine NH 2 CH
Quinone Alternative Reactions? Phloroglucinol Ascorbate RSH H Phenolic Coupling (polymerization) (Quinone) AA's, Strecker Degradation S R Mercaptan Trapping S 2 Aldehydes?
Fenton Products xidation of alcohols (major components) Ethanol rganic Acids Sugars Anything Reduced by S 2 Removes hydrogen peroxide
Reactivity of Hydroxyl Radical Extremely reactive xidizes the first molecule it encounters xidation products are determined by concentration Antioxidants cannot protect against this oxidation
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 Color development Aroma if the amounts exceed color reactions, S 2 binding capacityoxidized character
Ethanol to Acetaldehyde Ethanol C H 3 C H2 H Hydroxyl radical C H 3 C H 2 C H 3 C H Acetaldehyde C H 3 C H + H
Formation of Branched Aldehydes Fenton oxidation of alcohols CH CH CH
xidation of Wine Acids (Alcohols) to Carbonyls Pyruvic bserved in wine Reacts with anthocyanins to make wine pigments H CH 3 Lactic Acid (or Malic) H 2 2 Fe +2 CH 3 Pyruvic Acid Glyoxylic bserved in wine Condenses with flavan-3-ols H Tartaric Acid H 2 2 Fe +2 H Hydroxymalonic CH Glyoxylic Acid
Loss of isoprenoids by oxidation Ferreira, A., ACA 513: 169 (04) the levels of all nor-isoprenoids decreased after a certain concentration of oxygen was consumed, e.g. 10 mg /L
Glycerol xidation H Two novel oxidation products Not previously reported in wine Glycerol Can they affect wine color, etc? They do slightly darken red wine when added + H 2 2 H + Fe +2 Dihydroxyacetone H Glyceraldehyde Laurie and Waterhouse, Journal of Agricultural and Food Chemistry, May 2006
Aldehyde Coupling of Phenolics Importance of aldehydes in tannin coupling H + H H + H + H C + -H + model H H H H
Glyceraldehyde Bridged Cmpds H H H R H R= H H H H R H + Me Me -Glucose
Aldehyde Pigment Reactions D-ring formation by acetaldehyde and pyruvate H + Glu R1 R2 or H H R + Glu R1 R2 R = H,
Sotolon xidation product rigin from 2-keto butyric acid? C 2 H + H 2-ketobutyric acid C 2 H Pham JAFC 43: 2616 (95) H sotolon
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
Sotolon from xidation Yeast lees minimize formation Lavigne, JAFC 56: 2688 (08)
Fenton Routes Trapping Agent ethanol a b Hydroperoxyl Radical of Ethanol c Hydroxyl radical Ethoxyl radical d e Hydrogen peroxide acetaldehyde Hydroperoxyl radical catechol
Fenton Inhibition in Model Wine Inhibition by Phenolics 1.1 Acetaldehyde (Norm) 0.9 0.7 0.5
Fenton Inhibition by Cinnamates Acetaldehyde (Norm) 1.1 0.9 0.7 R 1 R R 2 1 R 2 (Hydro)Cinnamic Acid: R 1 /R 2 = H (Hydro)Caffeic Acid: R 1 /R 2 = 0.5 NP HCinn HCaff Cinn Caff
xidation Product of Cinnamates Two Products Coumaric, Caffeic or Ferulic
Ferulic Products H H Me Et H Me H +, Me H Me H +, Et H Me
Mechanism of Ethoxyl Trapping C H Me C H H Me Fe(III) Fe(II) C 2, H + C + H Me H Me
Cinnamates-Major Free Radical Traps Previously predicted by basic studies Pulse radiolysis generation of radicals First observation in food May be important in many food systems Cinnamates are ubiquitous
Acknowledgements American Vineyard Foundation CCGPREV Nomacorc SA Collaborators: University of Copenhagen Nick Gislason, Screaming Eagle
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