monitoring acids and ph in winemaking mike miller the reluctant chemist
TRANSCRIPT
Monitoring Acids and pH in Winemaking
Mike MillerThe 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?
• 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
• 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?
• 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?
• 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?
• Harvest monitoring• Upon receipt• After primary fermentation• After malolactic fermentation• After any process• Periodically