VWT 272 Class 7 Quiz 5 Number of quizzes taken 19 Min 2 Max 30 Mean 19.5 Median 23 Mode 24
Lecture 7 Other (Smelly) Sulfur Compounds He that lives upon hope will die farting. Benjamin Franklin (1706-1790)
Plan of Study Review The Sulfur Dioxide Family Sulfite Bisulfite Molecular SO 2 Free vs. Bound vs. Total SO 2 additions Vineyard Sulfur Additions S vs. Bordeaux Mixture Hydrogen Sulfide Causes Vineyard S, yeast nutrition, or??? Prevention Removal CuSO 4 vs. wishing Disulfide
The (SO 2 ) Family Equilibrium Sulfite Bisulfite Molecular SO 2 SO 3 2- HSO 3 - SO 2 (aq) The concentration of each family member depends upon ph
Sulfite ion (SO 3 2- ) At wine ph is virtually nonexistent 1 to 3 μm < 0.01% at ph 3.4 Is a good Antioxidant (O 2 grabber) BUT requires much higher ph
Bisulfite ion (HSO 3- ) At wine ph is Most common form 94.4% at ph 3.0 99.4% at ph 4.0 Is not a good Antioxidant (O 2 grabber) Is not a good Antimicrobial Binds with the carbonyl oxygen in Acetaldehyde Glucose Keto acids Pyruvate Inhibits polyphenol oxidase
Acetaldehyde Produced by Saccharomyces cerevisiae Then Re-utilized by the yeast Malolactic bacteria degrade Acetaldehyde during MLF Oxidation Coupled chemical reaction O 2 reacts with a phenol to make Quinone + Hydrogen Peroxide (H 2 O 2 ) Hydrogen Peroxide oxidizes Ethanol to Acetaldehyde
Bisulfite ion (HSO 3- ) Binds with the carbonyl oxygen in Acetaldehyde Binds with other carbonyl group containing molecules to form Bound SO 2
Molecular SO 2 At wine ph is present in small amounts 5.6% at ph 3.0 0.6% at ph 4.0 Is responsible for antimicrobial action Not ionic can pass through cell membranes Disrupt enzyme activity Disturb protein structure Reacts with Hydrogen Peroxide (H 2 O 2 ) to make Sulphate SO 4 2- before it can react with ethanol SO 2 + H 2 O 2 2H + + SO 4 2- Fast CH 3 CH 2 OH + H 2 O 2 CH 3 CHO + 2 H 2 O Slow
Molecular SO 2 The Table
Free vs. Bound SO 2 At wine ph Bound (BSO 2 ) is all SO 2 in the Bisulfite ion (HSO 3- ) form that is bound to Acetaldehyde Glucose Keto Acids Free (FSO 2 ) is all SO 2 in the Bisulfite ion (HSO 3- ) form that is NOT bound + all Molecular SO 2 Total SO 2 (TSO 2 ) = FSO 2 + BSO 2
Free SO 2 Addition Calculations Imprecise GUIDE for SO 2 Addition in Juice/Must Assume ~ 60 % of your added SO 2 will be bound (BSO 2 ) 100 mg added SO 2 /40 mg free SO 2 Concentration will drop rapidly to unmeasurable Damaged fruit will require significantly more SO 2
Free SO 2 Addition Calculations Imprecise GUIDE for SO 2 Addition in Wine ~ 50% of SO 2 Addition becomes quickly bound in young wines and wines below 60 mg/l TSO 2 100 mg added SO 2 / 50 mg free SO 2 ~ 30% of SO 2 Addition becomes quickly bound in wines between 60 mg/l and 100 mg/l TSO 2 100 mg added SO 2 / 70 mg free SO 2 ~ 15% of SO 2 Addition becomes quickly bound in older wines above 100 mg/l TSO 2 100 mg added SO 2 / 85 mg free SO 2 KMB has 0.576 g of SO 2 for every g of KMB
Free SO 2 Addition Calculations 1. Determine the amount of Molecular SO 2 you need and the volume of wine you will be sulfuring 2. Estimate the amount of binding that will occur after addition 3. Calculate the amount of Free SO 2 needed to get the required Molecular SO 2 from The Table or on-line calculator 4. Calculate the additional Free SO 2 needed given the Free SO 2 already in the wine 5. Use the correct concentration factor for the method of SO 2 addition (KMB vs. pure gas vs. 10% or 6% solution)
Where does Sulfur come from?
Where does Sulfur come from?
Vineyard Sulfur
Vineyard Sulfur Useful against Powdery Mildew (Uncinula necator) Since 1890 s spray intervals between 7 to 21 days Extremely good models of PM growth based upon temperatures between 70 and 85 F
Mutiple forms Vineyard Sulfur Dust S with average particle size of 20 to 45 microns applied dry Wettable S, 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 (CuSO 4 ) & Slacked Lime (Ca(OH) 2 )
Bordeaux Mixture
Hydrogen Sulfide (H 2 S) AKA: Reduced
Recipe to make something smelly replace an O with an S Hydrogen Sulfide fart/rotten egg 1 ppb 1,3-hexanediol odorless 3-mercaptohexanol Passion fruit 60 ppt
Where does H 2 S come from? Vineyard based Elemental S residue More S more H 2 S Mechanism not well understood S S 2- Highly yeast strain dependant Takes place on cell wall of yeast Younger yeast cells produce more S 2- Higher alcohol produces more S 2- 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
It is a (Protein) Rave!
Where does H 2 S come from? Inappropriate Yeast nutrition Yeast leak H 2 S when they make 2 amino acids Methionine and Cysteine Yeast make all organic S containing compounds from the S containing amino acids
Where does H 2 S come from? Inappropriate Yeast nutrition Yeast release H 2 S 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 H 2 S come from? High solids fermentations High temperature fermentations Lees contact Release from S containing compounds in yeast Loosley Bound to compounds in wine Poorly understood mechanism???
Removing H 2 S The Smart Way Copper Sulfate (CuSO 4 ) addition CuSO 4 Cu 2+ + SO 2-4 Cu 2+ + SO 2-4 + H 2 S CuS (s) + 2H + + SO 2-4 What matters is the Cu 2+ CuSO 4 available as: CuSO 4 (anhydrus) white powder CuSO 4 5(H 2 O) copper sulfate pentahydrate blue power 10% & 1% (as? (usually CuSO 4 )) Confirm with supplier
Removing H 2 S The Smart Way According to the TTB (27 CFR Ch 1 24.246) The quantity of copper sulfate added (calculated as copper) (Cu 2+ ) 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 Cu 2+ = 63.5 Molar Mass of CuSO 4 5(H 2 O) = 249.7 So 25.4% of CuSO 4 5(H 2 O) is Cu 2+ 100 mg CuSO 4 5(H 2 O) / 25.4 mg Cu 2+
Removing H 2 S The Smart Way The secret about Cu 2+ If there any yeast present, especially live yeast, they will capture large amounts of any remaining Cu 2+ left in the wine after addition
Calculation with Cu 2+ 1500 gal of Grenache with a serious H 2 S problem. Bench trials suggest that you need to add 0.5 mg/l Cu 2+. How much CuSO 4 5(H 2 O) do you add? 1500 gal x 3.785 L/1 gal x 0.5 mg Cu 2+ /L x 100 mg CuSO 4 5(H 2 O) / 25.4 mg Cu 2+ x 1 g CuSO 4 5(H 2 O)/ 1000 mg CuSO 4 5(H 2 O) = 11.2 g CuSO 4 5(H 2 O) 225 L of Chenin Blanc with slight reduction. Bench trials suggest that you need to add 0.2 mg/l Cu 2+. How much 1% Cu 2+ solution do you add? First confirm that the 1% is as 1% Cu 2+ (not 1% CuSO 4 5(H 2 O) 225L x 0.2 mg Cu 2+ /L x 100 ml Cu 2+ solution / 1 g Cu 2+ x 1 g Cu 2+ / 1000 mg Cu 2+ = 4.5 ml Cu 2+ solution
Removing H 2 S The Dumb Way Splash or run Oxygen through the wine Splashing will force the volatile H 2 S out of the wine O 2 will displace the S in the H 2 S 2H 2 S + O 2 2H 2 O + 2 S Run the risk of forming thiols/mercaptans from the H 2 S reacting with acetaldehyde.
Removing H 2 S The Dumb Way Remember the coupled reaction to form acetaldehyde (CH 3 CHO) 2H 2 S + CH 3 CHO HSCH 2 CH 2 SH + H 2 O Ethanedithiol Highly reactive Degrades into other thiols Smells like durian
Removing H 2 S The Dumb Way Ethanedithiol may degrade into: Compound Aroma Description Concentration in Wine (µg/l) Odor Threshold (µg/l) Methanethiol Cooked cabbage, 0 to 16 2 (Methyl mercaptan) rotten eggs Ethanethiol (Ethyl mercaptan) Onion, rubber, natural gas, fecal 0 to 12 1.1 None of the above compounds are easily removed from wine SOME react with Cu 2+ slowly (months) Thiols can form an equilibrium with disulfides
Removing H 2 S The Dumb Way Thiols can form an equilibrium with disulfides Compound Aroma Description Concentration in Wine (µg/l) Odor Threshold (µg/l) Dimethyl disulfide Diethyl disulfide Cooked vegetable, strong onion Cabbage Strong onion, burnt rubber 0 to 22 29 0 to 80 4.3 Disulfides do not react with Cu 2+
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