Texas University

Document Sample
Texas University Powered By Docstoc
					  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?

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:4
posted:8/17/2011
language:English
pages:19