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Sulfur Compounds in Wine. Linda Bisson Department of Viticulture and Enology. Introduction to S-Containing Faults. Why Are Sulfur Compounds a Problem?. Low thresholds of detection Negatively-associated aromas Chemical reactivity Difficulty in removal Difficulty in masking.

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sulfur compounds in wine

Sulfur Compounds in Wine

Linda Bisson

Department of Viticulture and Enology

why are sulfur compounds a problem
Why Are Sulfur Compounds a Problem?
  • Low thresholds of detection
  • Negatively-associated aromas
  • Chemical reactivity
  • Difficulty in removal
  • Difficulty in masking
the classic sulfur fault descriptors
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
the sulfur taints
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
sources of sulfur compounds
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
timing of sulfur fault formation
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
hypotheses to explain s taint formation
Hypotheses to Explain S-Taint Formation
  • Correlated with H2S formation during the primary fermentation
  • Correlated with late H2S formation (peak 2) but not with H2S 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
problems with previous studies
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
why is h 2 s formed
Why is H2S formed?
  • Off-shoot of metabolism
  • Reductive environment
  • Signaling molecule
hydrogen sulfide formation off shoot of metabolism
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 H2S
  • Also a stress response
  • Strain variation
stress response reduction pathway remains operational
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
slide14

Sulfate Reduction Pathway

SO4

SUL1, SUL2

SO4

MET3

Adenylylsulfate

MET14

H2S

Phosphoadenylylsulfate

MET16 (1,8,20,22)

Sulfite

MET10 (1,5?,8,20)

Sulfide

MET17/25/15

Cysteine Cystathionine Homocysteine Methionine

CYS3

CYS4

MET6

hydrogen sulfide formation reductive environment
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
hydrogen sulfide formation reductive environment16
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
hydrogen sulfide formation signaling molecule
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
current understanding of h 2 s formation
Current Understanding of H2S Formation
  • Nitrogen levels not well-correlated with H2S formation, but generally see increased H2S at lower nitrogen
  • Tremendous strain variation in H2S production
  • Can get H2S with high nitrogen
  • Get more H2S with higher solids content
  • Get more H2S with unsound fruit
factors impacting h 2 s formation
Factors Impacting H2S Formation
  • Level of total nitrogen
  • Level of methionine relative to total nitrogen
  • Fermentation rate
  • Use of SO2
  • Vitamin deficiency
  • Presence of metal ions
  • Inorganic sulfur in vineyard
  • Use of pesticides/fungicides
  • Strain genetic background
timing of formation of h 2 s21
Timing of Formation of H2S
  • 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
higher sulfides23
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
volatile sulfur compounds
Volatile Sulfur Compounds
  • Methanethiol: CH3-SH
  • Ethanethiol: C2H5-SH
  • Dimethyl sulfide: CH3-S-CH3
  • Dimethyl disulfide: CH3-S-S-CH3
  • Dimethyl trisulfide: CH3-S-S-S-CH3
  • Diethyl sulfide: C2H5-S-C2H5
  • Diethyl disulfide: C2H5-S-S-C2H5
sources of higher sulfides
Sources of Higher Sulfides
  • S-Containing Amino Acids
  • S-Containing Vitamins and Co-factors
  • Glutathione (Cysteine-containing tripeptide involved in redox buffering)
slide26

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
slide27

Defining Metabolic Behaviors Resulting in Taint Formation

  • 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
Defining Metabolic Behaviors Resulting in Taint Formation
  • 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
defining metabolic behaviors resulting in taint formation29
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
defining metabolic behaviors resulting in taint formation30
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
understanding the interface between metabolite production and wine chemistry and composition
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
sulfur compound flight 1 spiked compounds
Sulfur Compound Flight #1Spiked Compounds
  • Glass 1: Control Wine (Cabernet Sauvignon)
  • Glass 2: Hydrogen sulfide H2S
  • Glass 3: Dimethyl sulfide CH3-S-CH3
  • Glass 4: Dimethyl trisulfide: CH3-S-S-CH3
  • Glass 5: Diethyl sulfide: C2H5-S-C2H5
  • Glass 6: Diethyl disulfide: C2H5-S-S-C2H5
sulfur compound flight 1 spiked compounds33
Sulfur Compound Flight #1Spiked 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
sulfur compound flight 2 taints produced late in fermentation
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
sulfur compound flight 2 spiked compounds
Sulfur Compound Flight #2Spiked 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
bm 45
BM 45:
  • Isolated in Montalcino
  • Produces high polyphenol reactive polysaccharides = mouth feel
  • Has high nitrogen requirements and can produce H2S
  • Aroma characteristics: fruit jam, rose, cherry, spice, anise, cedar and earthy