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Sulfur Compounds in Wine Linda Bisson Department of Viticulture and Enology.

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Presentation on theme: "Sulfur Compounds in Wine Linda Bisson Department of Viticulture and Enology."— Presentation transcript:

1 Sulfur Compounds in Wine Linda Bisson Department of Viticulture and Enology

2 Introduction to S-Containing Faults

3 Why Are Sulfur Compounds a Problem?  Low thresholds of detection  Negatively-associated aromas  Chemical reactivity  Difficulty in removal  Difficulty in masking

4 The Classic Sulfur Fault Descriptors  Rotten egg  Fecal  Rubber/Plastic tubing  Burnt match  Burnt molasses  Burnt rubber  Rotten vegetable: cauliflower, cabbage, potato,  asparagus, corn  Onion/Garlic  Clam/Tide pool  Butane/Fuel/Chemical

5 The Sulfur Taints  Hydrogen sulfide  Higher sulfides Dimethyl (Diethyl) sulfide Dimethyl disulfide  Mercaptans Methyl (Ethyl) mercaptan  Thioesters Methyl (ethyl) thioacetate  Other S-amino acid metabolites Thioethers Cyclic and heterocyclic compounds

6 Sources of Sulfur Compounds Non-biological Elemental sulfur S-containing pesticides Biological Sulfate/Sulfite reduction and reduced sulfide reactions S-containing amino acid metabolism S-containing vitamins and cofactors degradation Glutathione metabolism and degradation S-containing pesticides degradation Elemental sulfur

7 Timing of Sulfur Fault Formation  Primary Fermentation Early: Hydrogen Sulfide  Primary Fermentation Late: Hydrogen Sulfide  Post Fermentation: Hydrogen Sulfide or Sur Lie Faults  Bottling: S-fault development

8 Hypotheses to Explain S-Taint Formation  Correlated with H 2 S formation during the primary fermentation  Correlated with late H 2 S formation (peak 2) but not with H 2 S formation during primary fermentation  Associated with S-containing amino acid levels during primary fermentation  Due to degradation of S-containing metabolites during yeast lees aging, but not related to levels of these compounds present in the initial juice  Yeast strain most important  Juice composition most important

9 Problems with Previous Studies  Lack of control of all variables  Invalid comparisons (too many variables)  Confounding factors not considered to be important  Differences in strains and conditions used  Driving reactions by having an excess of precursors, beyond anything found in juices or wines

10 HYDROGEN SULFIDE

11 Why is H 2 S formed?  Off-shoot of metabolism  Reductive environment  Signaling molecule

12 Hydrogen Sulfide Formation: Off- Shoot of Metabolism  Due to release of reduced sulfide from the enzyme complex sulfite reductase  Reduction of sulfate decoupled from amino acid synthesis  Sulfate reduction regulated by nitrogen availability  Lack of nitrogenous reduced sulfur acceptors leads to excessive production of reduced sulfate and release as H 2 S  Also a stress response  Strain variation

13 Stress Response: Reduction Pathway Remains Operational  Need cysteine for glutathione (tripeptide cytoplasmic redox (electron) buffer  Need methionine for S- adenosylmethionine and one carbon transfers needed for ethanol tolerance

14 Sulfate Reduction Pathway SUL1, SUL2 SO 4 Adenylylsulfate Phosphoadenylylsulfate Sulfite Sulfide Cysteine Cystathionine Homocysteine Methionine MET3 MET14 MET16 (1,8,20,22) MET10 (1,5?,8,20) MET17/25/15 MET6 CYS4CYS3 H2SH2S

15 Hydrogen Sulfide Formation: Reductive Environment  Biological energy is obtained from recapture of light (carbon bond) energy, from proton movements and from electron movements  Cell is dealing with an excess of electrons that exceeds buffering capacity  Many electrons can be used to reduce a single sulfate molecule restoring the proper balance of cytoplasmic electrons

16 Hydrogen Sulfide Formation: Reductive Environment  Tank dimensions leading to stratification of electron gradients  Settling of yeast cells  Chemical composition of juice  Oxygen level and content of juice

17 Hydrogen Sulfide Formation: Signaling Molecule  Hydrogen sulfide coordinates population metabolic activities: shuts down respiration in favor of fermentation, coordinating population of cells in fermentation  Hydrogen sulfide inhibits respiration of a variety of organisms: allows more rapid domination of fermentation  Explains selective pressure for high sulfide producers in the wild

18 Current Understanding of H 2 S Formation  Nitrogen levels not well-correlated with H 2 S formation, but generally see increased H 2 S at lower nitrogen  Tremendous strain variation in H 2 S production  Can get H 2 S with high nitrogen  Get more H 2 S with higher solids content  Get more H 2 S with unsound fruit

19 Factors Impacting H 2 S Formation  Level of total nitrogen  Level of methionine relative to total nitrogen  Fermentation rate  Use of SO 2  Vitamin deficiency  Presence of metal ions  Inorganic sulfur in vineyard  Use of pesticides/fungicides  Strain genetic background

20 Timing of Formation of H 2 S Brix Time H2SH2S

21 Timing of Formation of H 2 S Early (first 2-4 days): due to N/vitamin shortage, electron imbalance, signaling Late (end of fermentation): due to degradation of S-containing compounds Sur lie (post-fermentation aging): due to autolysis In Bottle: screw cap closures: return from an altered chemical form

22 HIGHER SULFIDES

23 Higher Sulfides  Emerge late in fermentation and during sur lie aging  Release of compounds during entry into stationary phase by metabolically active yeast  Come from degradation of sulfur containing amino acids  Biological  Chemical  From reaction of reduced sulfur intermediates with other cellular metabolites?  Formed chemically due to reduced conditions?  Degradation of cellular components: autolysis

24 Volatile Sulfur Compounds  Methanethiol: CH 3 -SH  Ethanethiol: C 2 H 5 -SH  Dimethyl sulfide: CH 3 -S-CH 3  Dimethyl disulfide: CH 3 -S-S-CH 3  Dimethyl trisulfide: CH 3 -S-S-S-CH 3  Diethyl sulfide: C 2 H 5 -S-C 2 H 5  Diethyl disulfide: C 2 H 5 -S-S-C 2 H 5

25 Sources of Higher Sulfides  S-Containing Amino Acids  S-Containing Vitamins and Co-factors  Glutathione (Cysteine-containing tripeptide involved in redox buffering)

26  S-amino acid catabolism  Vitamin/Co-factor interactions and metabolism  Glutathione turnover and reactions  Metabolic roles of sulfate reduction Defining Metabolic Behaviors Resulting in Taint Formation

27  S-amino acid catabolism  Degradation of methionine and cysteine: methional and methionol  Chemical reaction products of methionine and cysteine: stress resistance  Influence of wine composition and chemistry on yeast behavior  Vitamin/Co-factor interactions and metabolism  Glutathione turnover and reactions  Metabolic roles of sulfate reduction Defining Metabolic Behaviors Resulting in Taint Formation

28  S-amino acid catabolism  Vitamin/Co-factor interactions and metabolism  Role of thiamin  Role of S-adenosylmethionine  Glutathione turnover and reactions  Metabolic roles of sulfate reduction

29 Defining Metabolic Behaviors Resulting in Taint Formation  S-amino acid catabolism  Vitamin/Co-factor interactions and metabolism  Glutathione turnover and reactions  Role in stress response: prevention of oxidative damage  Impact of nitrogen level on metabolism  Biological turnover of ‘reacted’ glutathione  Metabolic roles of sulfate reduction

30 Defining Metabolic Behaviors Resulting in Taint Formation  S-amino acid catabolism  Vitamin/Co-factor interactions and metabolism  Glutathione turnover and reactions  Metabolic roles of sulfate reduction  Stress response:  Prevention of oxidative damage  Role in ethanol tolerance  Environmental/metabolic detoxification  Banking on reactivity to inactivate a toxic substance  Metabolic demands

31 Understanding the Interface between Metabolite Production and Wine Chemistry and Composition  What environmental conditions impact S- compound metabolic activities?  Separating a biological response from a chemical one  Control the metabolites  Control the chemistry

32 Sulfur Compound Flight #1 Spiked Compounds Glass 1: Control Wine (Cabernet Sauvignon) Glass 2: Hydrogen sulfide H 2 S Glass 3: Dimethyl sulfide CH 3 -S-CH 3 Glass 4: Dimethyl trisulfide: CH 3 -S-S-CH 3 Glass 5: Diethyl sulfide: C 2 H 5 -S-C 2 H 5 Glass 6: Diethyl disulfide: C 2 H 5 -S-S-C 2 H 5

33 Sulfur Compound Flight #1 Spiked Compounds G 1: Control Wine (Cabernet Sauvignon) G2: Hydrogen sulfide: rotten egg G 3: Dimethyl sulfide: cabbage, cooked corn, asparagus, canned vegetable G 4: Dimethyl trisulfide: meaty, fishy, clams, green, onion, garlic, cabbage G 5: Diethyl sulfide: garlic, onion G 6: Diethyl disulfide: overripe onion, greasy, garlic, burnt rubber, manure

34 Sulfur Compound Flight #2: Taints produced late in fermentation Glass 1: Control Wine (Cabernet Sauvignon) Glass 2: Ethanethiol Glass 3: Mercapto -2- methyl propanol (Methionol) Glass 4: Methyl thiopropionaldehyde (Methional) Glass 5: Mercapto-3-methyl butanol Glass 6: BM45 French Colombard

35 Sulfur Compound Flight #2 Spiked Compounds G 1: Control Wine (Cabernet Sauvignon) G 2: Ethanethiol: onion, rubber, natural gas G 3: Methionol: cauliflower, cabbage, potato G 4: Methional: musty, potato, onion, meaty G 5: Mercapto-3-methyl butanol: meaty G 6: French Colombard: reduced

36 BM 45:  Isolated in Montalcino  Produces high polyphenol reactive polysaccharides = mouth feel  Has high nitrogen requirements and can produce H 2 S  Aroma characteristics: fruit jam, rose, cherry, spice, anise, cedar and earthy


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