Transcript Monitoring Acids and pH in Winemaking

Monitoring Acids and pH
in Winemaking
Mike Miller
The Reluctant Chemist
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
Why are pH and TA important?
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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
The major winemaking acids
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Tartaric
Malic
Citric
L-Lactic
Succinic
What are the optimum levels?
• pH: red @ 3.3 – 3.6
white @ 3.1 – 3.4
• TA: red @ 6 – 8 g/L
white @ 7 – 9 g/L
How can I increase TA levels?
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Add tartaric acid
Add DL-malic acid
Add L-malic acid
Add L-lactic acid
Add citric acid
Add fumaric acid
Add sorbic acid
How can I decrease acidity levels?
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Maloalcoholic fermentation
Deacidify with calcium carbonate
Deacidify with potassium bicarbonate
Treat with Acidex (takes two steps)
Conduct MLF
Blend
Stabilize
Ameliorate
How do I adjust pH?
• Ion exchange
• Sulfuric acid?
What about those acids I don’t want?
• D-Lactic acid
• Acetic acid
And that other acid?
• Sulfurous acid, a.k.a. SO2
SO2 Chemistry
SO2 + H2O = HSO3-1 + H+
How can I best control pH, Acids, and
Acidity?
• Monitor
Wine and winemaking problems
Name of Problem
Flaw
Fault
Caused by
faulty
Winemaking
Presence of reduced sulfur compounds (e.g., H2S)
20%
80%
20%
Presence of acetaldehyde
5%
95%
100%
MLF in bottled wine
40%
60%
80%
Yeast Fermentation in bottled wine
50%
50%
100%
Presence of ethyl acetate
5%
95%
10%
Inadequate settling of white juice
80%
20%
100%
Presence of tyrene (T.C.A. = corkiness)
20%
80%
0%
Presence of 2,3-ethoxy-3,4-hexadiene (geranium)
5%
95%
90%
Presence of volatile acidity – acetic acid
80%
20%
80%
Presence of diacetyl
90%
10%
50%
Brettanomyces contamination
80%
20%
0%
Additive overuse (SO2, sorbate,etc.)
90%
10%
100%
When should I monitor?
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Harvest monitoring
Upon receipt
After primary fermentation
After malolactic fermentation
After any process
Periodically