Sulfur Dioxide Measurement and Management Chik Brenneman Anita

Sulfur Dioxide Measurement and Management Chik Brenneman Anita Oberholster

Sulfur Dioxide Measurement and Management Introduction • What is sulfur dioxide? • Why is it important • Practical considerations for winemaking/Management during aging • Measurement techniques • What does it mean? • Alternatives

Sulfur Dioxide Measurement and Management Overview • Chemical antioxidant and inhibitor of microbial activity • Labeling requirements • Industry wide trend for reduction in use

Sulfur Dioxide Measurement and Management Chemical antioxidant • Inhibitor of browning reactions in juice • Polyphenol oxidase • Cultivar, juice vs. must • Typical additions of 30 -50 mg/L • Laccase is minimally affected • Residual laccase activity in wine can cause browning • Participates in binding reactions • Aldehydes, e. g. acetaldehyde • Anthocyanins

Sulfur Dioxide Measurement and Management Inhibitor of microbial activity • Juice – levels for enzyme inhibition are sufficient for inhibition or significant reduction in native flora • In General • Bacteria are sensitive • Yeast are less sensitive • Sensitivity varies by organism

Sulfur Dioxide Measurement and Management Sulfur Dioxide Species • Molecular (SO 2) • Bisulfite (HSO 3 -) • Sulfite (HSO 32 -)

Sulfur Dioxide Measurement and Management Sulfur Dioxide Species • Molecular (SO 2) • Anti-microbial • Peroxide scavenger • Volatile

Sulfur Dioxide Measurement and Management Sulfur Dioxide Species • Bisulfite (HSO 3 -) • Binding form (Hydroxysulfonates • Acetaldehyde, acetaldehyde, glucose, quinones, anthocyanins

Sulfur Dioxide Measurement and Management Sulfur Dioxide Species • Sulfite (HSO 32 -) • Anti-oxidant form • Under wine conditions, this reaction is not favoreddue to the low concentrations present • Peroxide scavenging of the molecular form causes retardation of acetaldehyde formation or browing

Sulfur Dioxide Measurement and Management Relationship with p. H • Measure free H+ ions • p. H = -log [H+] • Why is knowing the p. H important? • Microbial stability • Effectiveness of SO 2 • Molecular SO 2 is the form effective against microorganisms

Sulfur Dioxide Measurement and Management

Sulfur Dioxide Measurement and Management Free and Total Sulfur Dioxide • Total – Bound = Free • Exist as a dynamic equilibrium • Post fermentation goals to add and stabilize the equilibrium

Sulfur Dioxide Measurement and Management Practical Considerations • Understand the relationship with p. H • Volatility and sensory thresholds • Balancing acidity independent of p. H

Sulfur Dioxide Measurement and Management Inhibitor of microbial activity

Sulfur Dioxide Measurement and Management p. H versus free sulfur dioxide The percentage of SO 2 forms in solution at specific p. H values* Free SO 2 for Molecular 0. 825 mg/L p. H SO 2 Bisulfite Sulfite molecular 2. 7 10. 50 89. 5 0. 00283 7. 9 2. 8 8. 54 91. 5 0. 00364 9. 7 2. 9 6. 90 93. 1 0. 00467 12. 0 3. 0 5. 56 94. 4 0. 00596 14. 8 3. 1 4. 47 95. 5 0. 00759 18. 5 3. 2 3. 58 96. 4 0. 00964 23. 1 3. 3 2. 87 97. 1 0. 0122 28. 8 3. 4 2. 29 97. 7 0. 0155 36. 0 3. 5 1. 83 98. 2 0. 0196 45. 1 3. 6 1. 46 98. 5 0. 0248 56. 5 3. 7 1. 16 98. 8 0. 0312 71. 1 3. 8 0. 924 99. 0 0. 0394 89. 3 3. 9 0. 736 99. 2 0. 0497 112. 0 4. 0 0. 585 99. 4 0. 0627 141. 0 *Boulton, et. al. Principles and Practices of Winemaking, 1985

Sulfur Dioxide Measurement and Management Other Practical Considerations • Cleaning • Sanitation • Segregation of blends

Sulfur Dioxide Measurement and Management Sources of Sulfur Dioxide • Potassium Metabisulfite • Powder form • Effervescent form • Gas • Concentration specific solutions

Sulfur Dioxide Measurement and Management Calculating SO 2 Additions • KMBS comes as a powder, it is a salt of sulfur dioxide. • 57% is ‘active’ • Potency decreases over time (temperature/humidity) • Example: add 50 ppm to 100 L • (Desired addition (g/L)* volume (L))/0. 576= g KMBS • 0. 050 (g/L)* 100 (L) = 8. 6 g KMBS 0. 576

Sulfur Dioxide Measurement and Management Addition Strategy • First additions for the prevention of and/or at the completion of the MLF • 30 mg/L for whites, 50 mg/L for reds • Test at 2 -3 weeks as equilibrium is established • Additional additions are based on free and total results • Something is better than nothing

Sulfur Dioxide Measurement and Management Sulfur dioxide analysis (free and bound) • • • Ripper Iodine Titration Ripper Iodate Titration Aeration Oxidation Monier-Williams Fiastar FOSS

Sulfur Dioxide Measurement and Management Measurement Methods • Each method has its limitations • Hydrolysis of the hydroxy-sulfonate can affect interpretation of the free form

Sulfur Dioxide Measurement and Management Ripper Iodine Titration • Re. Dox titration • End point seen using starch indicator/redox electrode • Useful for Free and Total SO 2

Sulfur Dioxide Measurement and Management Ripper Iodine Titration • Limitations • Iodine degradation • Starch degradation • Endpoint recognition • Interfering compounds • Polyphenols • Ascorbate

Sulfur Dioxide Measurement and Management Ripper Iodate Titration • Iodate stability • Iodide-Starch indicator • Iodine produced in situ

Sulfur Dioxide Measurement and Management Aeration-Oxidation (Vacuum aspiration) • Air Aspiration/Nitrogen sweeping • SO 2 volatilized and bubbled through a peroxide trap • Sulfuric acid titrated with Na. OH • Useful for Free and Total

Sulfur Dioxide Measurement and Management Aeration-Oxidation (Vacuum aspiration) • Limitations • • Carrier gas flow rates should be standardized Glassware/Condenser requirements Anti-foam is recommended Some bound SO 2 can be released in the acidification step

Sulfur Dioxide Measurement and Management Monier-Williams (AOAC sanctioned) • Set up is similar to A-O • Sample size consideration • Reflux is 1. 75 hours

Sulfur Dioxide Measurement and Management Fiastar • • • Colorimetric endpoint High volume throughput Up to 200 mg/L range of detection Cost $20 -30 K Maintenance is key

Sulfur Dioxide Measurement and Management FOSS • FTIR scan of both the liquid and a gaseous sample. • Secondary method • Fast results • FTIR support on line

Sulfur Dioxide Measurement and Management Alternatives to sulfur dioxide • Alternatives tend to address single variables • Just say no (more than necessary) • Reacting to ‘real’ number • Clean fruit, good sanitation practices and some tolerance to higher volatile acidity

Sulfur Dioxide Measurement and Management Alternatives to sulfur dioxide • • Lysozyme Velcorin Ascorbic acid Ozone Ultrasound UV light Low electrical current (LEC) Pressure

Sulfur Dioxide Measurement and Management Summary • Powerful tool in traditional winemaking • Prize for a better substitute remains unclaimed • Use lends to predicable stability in both opened and unopened bottles of wine

Questions?