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?
Monitor

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