VWT 272Class 11

Quiz 10

Number of quizzes taken 20

Min 25

Max 30

Mean 29.8

Median 30

Mode 30

Lecture 11Other (Smelly) Sulfur Compounds

He that lives upon hope will die farting.

Benjamin Franklin (1706-1790)

Plan of Study• Vineyard Sulfur Additions

– S vs. Bordeaux Mixture

• Amino Acids & Proteins– Structures

• Hydrogen Sulfide– Causes

• Vineyard S, yeast nutrition, or ???

– Prevention

– Removal• CuSO4 vs. wishing

• Thiols & Disulfides

Where does Sulfur come from?Java, Indonesia

Where does Sulfur come from?Alberta Oil Sands, Canada

Vineyard Sulfur

Vineyard Sulfur• Useful against Powdery Mildew (Uncinula necator)

– Used since 1890’s

– Spray intervals between 7 to 21 days

– Extremely good models of PM growth based upon temperatures between 70° and 85° F

Vineyard Sulfur

• Mutiple forms

– Dust – S with average particle size of 20 to 45 microns

• applied dry

– Wettable –S plus dispersants and surfactants

• applied wet or dry

– Micronized – S with average particle size of 5 to 25 microns

• applied wet or dry

• Often discontinued when grapes reach 12 °Brix

• Problem if residue in must > 1 to 10 mg/L

Powdery vs. Downy

• Powdery Mildew on Grapes– Found everywhere in California– Controlled by Sulfur and other

fungicides

• Downy Mildew on Grapes– From Plasmopara viticola– Found in areas with spring & summer

rainfall at temperatures above 50° F– Controlled with “Bordeaux Mixture”

• Copper Sulfate (CuSO4) & Slacked Lime (Ca(OH)2)

Bordeaux Mixture

Hydrogen Sulfide (H2S)

AKA: “Reduced”

Recipe to make something smelly…replace an O with an S

Hydrogen Sulfidefart/rotten egg1 ppb

3-mercaptohexanolPassion fruit60 ppt

1,3-hexanediolodorless

Where does H2S come from?

• Vineyard based Elemental S residue

– More S leads to more H2S in the wine

– Mechanism not well understood

• S → S2- (sulfide)– Highly yeast strain dependant

– Takes place on cell wall of yeast

– Younger yeast cells produce more S2-

– Higher alcohol produces more S2-

– Amino acid Cysteine may be important

A Brief Detour into Amino Acids

• A class of compounds that have a specific spine and various side chains

A Brief Detour into Amino Acids

A Brief Detour into Amino Acids• Amino acids link together with “Peptide

Bonds” to form Peptides

• Peptides link to form polypeptides

A Brief Detour into Amino Acids• Polypeptides link to form the “Primary

Structure” of proteins

• The “Primary Structure” folds and packs into complex forms like helices and pleated sheets

From Amino Acids to Proteins

From Proteins to the Nobel Prize

Where does H2S come from?

• “Inappropriate” Yeast nutrition– Yeast “leak” H2S when they make 2 amino acids

• Methionine and Cysteine

• Yeast make all organic S containing compounds from the S containing amino acids

Where does H2S come from?

• “Inappropriate” Yeast nutrition

– Yeast “release” H2S when they use S containing amino acids to make other necessary building blocks

– Vitamin deficiency

• Biotin deficiency– Yeast need ~ 1 μg/L

• Pantothenate deficiency– Yeast need ~ 50 μg/L

Where (else) does H2S come from?

• High solids fermentations

• High temperature fermentations

• Lees contact– Release from S containing

compounds in yeast

• Loosely “Bound” to compounds in wine– Poorly understood mechanism

• ???

Removing H2S – The Smart Way

• Copper Sulfate (CuSO4) additionCuSO4 → Cu2+ + SO4

2-

Cu2+ + SO42- + H2S → CuS (s) + 2H+ + SO4

2-

– What matters is the Cu2+

• CuSO4 available as:– CuSO4 (anhydrus)

• white powder

– CuSO4●5(H2O) copper sulfate pentahydrate• blue power

• 10% & 1% (as ? (usually CuSO4))

• Confirm with supplier

Removing H2S – The Smart Way

• According to the TTB (27 CFR Ch 1 24.246)

– “The quantity of copper sulfate added (calculated as copper) (Cu2+) must not exceed 6 parts copper per million parts of wine (6.0 mg/L). The residual level of copper in the finished wine must not exceed 0.5 parts per million (0.5 mg/L).”

• Atomic Mass of Cu2+ = 63.5

• Molar Mass of CuSO4●5(H2O) = 249.7– So 25.4% of CuSO4●5(H2O) is Cu2+

– 100 mg CuSO4●5(H2O) / 25.4 mg Cu2+

Removing H2S – The Smart Way

• The “secret” about Cu2+

– If there any yeast present, especially live yeast, they will capture large amounts of any remaining Cu2+ left in the wine after addition

Calculation with Cu2+

• 1500 gal of Grenache with a serious H2S problem. Bench trials suggest that you need to add 0.5 mg/L Cu2+. How much CuSO4●5(H2O) do you add?

1500 gal x 3.785 L/1 gal x 0.5 mg Cu2+ /L x 100 mg CuSO4●5(H2O) / 25.4 mg Cu2+ x 1 g CuSO4●5(H2O)/ 1000 mg CuSO4●5(H2O) =

11.2 g CuSO4●5(H2O)

225 L of Chenin Blanc with slight “reduction”. Bench trials suggest that you need to add 0.2 mg/L Cu2+.

How much 1% Cu2+ solution do you add? – First confirm that the 1% is as 1% Cu2+ (not 1%

CuSO4●5(H2O) 225L x 0.2 mg Cu2+ /L x 100 ml Cu2+ solution / 1 g Cu2+ x 1 g Cu2+ / 1000 mg Cu2+ =

4.5 ml Cu2+ solution

Removing H2S – The Dumb Way

• Splash or run Oxygen through the wine

– Splashing will force the volatile H2S out of the wine

– O2 will displace the S in the H2S

2H2S + O2 2H2O + 2 S

• Run the risk of forming thiols/mercaptans from the H2S reacting with acetaldehyde.

Acetaldehyde Formation

Removing H2S – The Dumb Way

2H2S + CH3CHO → HSCH2CH2SH + H2O

• Ethanedithiol

– Highly reactive

• Degrades into other thiols

– Smells like durian

Your New BSF - Durian

Removing H2S – The Dumb Way

• Ethanedithiol can degrade into:

• None of the above compounds are easily removed from wine– SOME react with Cu2+ slowly (months)

Compound Chemical Formula

Aroma Description Concentration in Wine (µg/L)

Odor Threshold (µg/L)

Methanethiol (Methyl mercaptan) CH3SH

Cooked cabbage, rotten eggs

0 to 16 2

Ethanethiol (Ethyl mercaptan)

CH3CH2SHOnion, rubber,

natural gas, fecal0 to 12 1.1

Removing H2S – The Dumb Way

• Thiols can form an equilibrium with disulfides

• Disulfides do not react with Cu2+

Compound Chemical Formula

Aroma Description Concentration in Wine (µg/L)

Odor Threshold

(µg/L)Dimethyldisulfide

CH3SSCH3 Cooked vegetable, strong onion

Cabbage

0 to 22 29

Diethyl disulfide CH3CH2SSCH2CH3 Strong onion, burnt rubber

0 to 80 4.3

Next Week

• Spring Break!?!

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• Heat Stability

• Cold Stability