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Monitoring Acids and pH in Winemaking

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1 Monitoring Acids and pH in Winemaking
Mike Miller The Reluctant Chemist



4 5.0 g H2SO4/L = 7.5 g tartaric acid/L
TA Conversions % TA to g/L: multiply by 10 0.7 % TA = 7 g/L meq/L to g/L: divide by 13.33 100 meq/L = 7.5 g/L g H2SO4/L to g tartaric/L: multiply by 1.5 5.0 g H2SO4/L = 7.5 g tartaric acid/L

5 Why are pH and TA important?
pH ~ sourness pH and TA ~ astringency High pH = less red, more brown High pH = reduced capacity to mature High pH = more ionized components, more oxidation High pH = poor bentonite fining; greater protein instability High pH = greater susceptibility of bacterial growth pH + TA balance sugar + alcohol + glycerol

6 The major winemaking acids
Tartaric Malic Citric L-Lactic Succinic

7 What are the optimum levels?
pH: 3.3 – 3.6 3.1 – 3.4 TA: 6 – 8 g/L 7 – 9 g/L

8 How can I increase TA levels?
Add tartaric acid Add DL-malic acid Add L-malic acid Add L-lactic acid Add citric acid Add fumaric acid Add sorbic acid

9 How can I decrease acidity levels?
Maloalcoholic fermentation Deacidify with calcium carbonate Deacidify with potassium bicarbonate Treat with Acidex (takes two steps) Conduct MLF Blend Stabilize Ameliorate

10 How do I adjust pH? Ion exchange Sulfuric acid?

11 What about those acids I don’t want?
D-Lactic acid Acetic acid

12 And that other acid? Sulfurous acid, a.k.a. SO2

13 SO2 Chemistry SO2 + H2O = HSO3-1 + H+


15 How can I best control pH, Acids, and Acidity?

16 Wine and winemaking problems
Name of Problem Flaw Fault Caused by faulty Winemaking Presence of reduced sulfur compounds (e.g., H2S) 20% 80% Presence of acetaldehyde 5% 95% 100% MLF in bottled wine 40% 60% Yeast Fermentation in bottled wine 50% Presence of ethyl acetate 10% Inadequate settling of white juice Presence of tyrene (T.C.A. = corkiness) 0% Presence of 2,3-ethoxy-3,4-hexadiene (geranium) 90% Presence of volatile acidity – acetic acid Presence of diacetyl Brettanomyces contamination Additive overuse (SO2, sorbate,etc.)

17 When should I monitor? Harvest monitoring Upon receipt
After primary fermentation After malolactic fermentation After any process Periodically

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