Interactions and Use of Sulfur Dioxide in the Production of Wine Michael Sipowicz FSTC 606- Food Chemistry Texas A&M University Dr. Steve Talcott April 14, 2011 Sulfur Dioxide: An Introduction • Used in winemaking since at least the Middle Ages • From the beginning, benefits known but not understood • Still not fully understood today • Yeast can produce levels as high as 80ppm during fermentation • Measured as • “Free” SO2 – Unbound, Useful • “Total” SO2 – “Free” SO2 plus bound SO2 • U.S. Legal Limit is Finished Wine – 350ppm TSO2 Sulfur Dioxide: An Introduction • In the wine matrix, sulfur dioxide (SO2) and sulfite in ionic forms (sulfite SO32- or bisulfite HSO3-) are considered multi-action agents. • These three different forms do not occur in a wine simultaneously, but rather are each dominant at a given pH range. • The most important sulfur dioxide form with regard to antimicrobial attributes is the molecular SO2 form. Sulfur Dioxide: An Introduction MAIN USES IN WINE: • Inhibits Enzymatic Oxidation • Inhibits NonEnzymatic Oxidation • Antimicrobial Activity • Antioxidant Inhibits Enzymatic Oxidation • Leads to Browning products • Generally in juice and early must stages, of which the potential oxidative impact is greatest in white or rose’/blush wine production. • In this instance we are mostly concerned with Polyphenol oxidase but as well, in the case of unhealthy fruit, laccase Inhibits Nonenzymatic Oxidation • Sulfur Dioxide inhibits nonenzymatic oxidation of sugars and amino acids which is followed by browning plant tissues • Sulfites react with carbonyl groups of sugars thus preventing polymer formation and tissue browning. Antimicrobial Agent • Molecular SO2 is only form with antimicrobial activity. • Only form transported into organism’s cell • Exact mechanism is still unknown, but is believed to involve intercellular interactions between molecular SO2 and enzymes. • Broad-spectrum antimicrobial agent affecting a wide variety of microorganisms. • Broad range of sensitivity/tolerance. dependent. Antioxidant • Sulfites in wine can react directly with dissolved oxygen, albeit slowly. • Sulfites in wine can reduce hydrogen peroxide rapidly. • Sulfites in wine can react with quinones and other oxidative products. “Well Accepted” Oxidation Steps OH O O EtOH OH O2 + + H2O2 Acetaldehyde Step 1 Step 2 • Oxygen reacts with phenols to yield quinone and hydrogen peroxide • Hydrogen peroxide oxidizes ethanol to acetaldehyde A.L. Waterhouse, The Revolution of Wine Oxidation. Dept. of Viticulture & Enology,UC, Davis Fenton Reaction Ferrous iron Ferric iron + (II) (III) H + Fe + HO OH Fe + OH + H2O Hydrogen peroxide Hydroxyl radical A.L. Waterhouse, The Revolution of Wine Oxidation. Dept. of Viticulture & Enology,UC, Davis Oxygen Reduction in Wine O2 OO + H2O + RC=O RCOH R C OH RCHOH Fe+2 Fe+3 1 5 O2 HO O (Hydroperoxyl + OH HO (Hydroxyl radical) + H2O H+ radical) 2 Fe+3 H + OH OH O H 4 OH O O Fe+2 + HO OH (Semiquinone radical) (Hydrogen peroxide) 3 O O (Quinone) A.L. Waterhouse, The Revolution of Wine Oxidation. Dept. of Viticulture & Enology,UC, Davis Oxygen….An Anti-Oxidant? N2 Atmosphere Fe+3 + O2 RCHO + Fe+2 + H OO RHCOH RH C OH RCH2OH HO + H2O OH OH RCHO Fe+3 + H Fe+2 OH O SO2 HO OH H2O A.L. Waterhouse, The Revolution of Wine Oxidation. Dept. of Viticulture & Enology,UC, Davis Oxygen is an Antioxidant? • Peroxide/Iron Oxidation of Model Wine 350 300 Acetaldehyde 250 200 150 100 50 0 N2 Air Air, SO2 Air, SO2, Catechol A.L. Waterhouse, The Revolution of Wine Oxidation. Dept. of Viticulture & Enology,UC, Davis A FEW OF THE MANY ADDITIONAL REACTIONS Wine Color and Color Stability • Reacts with and “bleaches” pigmented compounds/anthocyanins . • Colored pigments are rendered colorless. • Primarily an issue with lighter colored wines but plays an important role in wine color stability in general. A FEW OF THE MANY ADDITIONAL REACTIONS Thiamin • Reacts with Thiamin ( Vitamin B1). • Required by yeast for healthy fermentations. • Reaction is irreversible • No longer available to yeast. A FEW OF THE MANY ADDITIONAL REACTIONS GOOD WINE GONE BAD…. • Let’s say you wanted to make a fruity, sweet wine…. ….without sterile filtration Fruity = NO ML Fermentation • Sulfur Dioxide is often added to prevent malolactic fermentation (ML) Sweet = NO YEAST Fermentation • Sorbic Acid is often added to inhibit yeast growth in wines bottled with residual sugar. PROBLEM : SO2 can react with Sorbic Acid • This reaction effectively depletes SO2 allowing the growth of ML bacteria. • ML Bacteria can metabolize the remaining sorbic acid. • This reaction results in spontaneous yeast and malolactic bacteria fermentations. A FEW OF THE MANY ADDITIONAL REACTIONS Ascorbic Acid • Sulfur Dioxide reacts with free oxygen in wine at a fairly slow pace. • Sulfur Dioxide reacts immediately with hydrogen peroxide. • Ascorbic acid reacts quite rapidly with free oxygen in wine yielding hydrogen peroxide. • SO2 and Ascorbic Acid are often used together to rapidly scavenge free oxygen in wine. • If however ascorbic acid is present with insufficient sulfur dioxide, ascorbic acid accelerates wine oxidation. Questions?
Pages to are hidden for
"Texas University"Please download to view full document