VWT 272 Class 7. Quiz 5. Number of quizzes taken 19 Min 2 Max 30 Mean 19.5 Median 23 Mode 24

Transcription

1 VWT 272 Class 7 Quiz 5 Number of quizzes taken 19 Min 2 Max 30 Mean 19.5 Median 23 Mode 24

2 Lecture 7 Other (Smelly) Sulfur Compounds He that lives upon hope will die farting. Benjamin Franklin ( )

3 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

4 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

5 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

6 Bisulfite ion (HSO 3- ) At wine ph is Most common form 94.4% at ph % 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

7 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

8 Bisulfite ion (HSO 3- ) Binds with the carbonyl oxygen in Acetaldehyde Binds with other carbonyl group containing molecules to form Bound SO 2

9 Molecular SO 2 At wine ph is present in small amounts 5.6% at ph % 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

10 Molecular SO 2 The Table

11 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

12 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

13 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 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 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 mg added SO 2 / 85 mg free SO 2 KMB has g of SO 2 for every g of KMB

14 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)

15 Where does Sulfur come from?

16 Where does Sulfur come from?

17 Vineyard Sulfur

18 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

19 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

20 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 )

21 Bordeaux Mixture

22 Hydrogen Sulfide (H 2 S) AKA: Reduced

23 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

24 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

25 A Brief Detour into Amino Acids A class of compounds that have a specific spine and various side chains

26 A Brief Detour into Amino Acids

27 A Brief Detour into Amino Acids Amino acids link together with Peptide Bonds to form Peptides Peptides link to form polypeptides

28 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

29 It is a (Protein) Rave!

30 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

31 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

32 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???

33 Removing H 2 S The Smart Way Copper Sulfate (CuSO 4 ) addition CuSO 4 Cu 2+ + SO 2-4 Cu 2+ + SO 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

34 Removing H 2 S The Smart Way According to the TTB (27 CFR Ch ) 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) = So 25.4% of CuSO 4 5(H 2 O) is Cu mg CuSO 4 5(H 2 O) / 25.4 mg Cu 2+

35 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

36 Calculation with Cu 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 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

37 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.

38 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

39 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 None of the above compounds are easily removed from wine SOME react with Cu 2+ slowly (months) Thiols can form an equilibrium with disulfides

40 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 to Disulfides do not react with Cu 2+

41 Spring Break! Next Week

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