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This article is from the WineMaking FAQ, by malak@CAM.ORG (Don Buchan) with numerous contributions by others.

28 Acid Balance: Why Is A Low Ph (3.0 To 3.5) Important To Winemaking?

For three reasons:

1. Chemical Stability: Wines become unstable at pHs above 3.50. One
result of this chemical instability is a severe effect on the wine's
pigment.

2. Biological Stability: Very few organisms (especially spoilage
organisms) can survive in an acidic environment (pH 2.90 - 3.50).
Because of this, fresh grapes or juices with pHs above 3.50 should be
avoided.

3. MOST IMPORTANTLY: Sulphite Additions: The amount of sulphite which
should be added to a must to achieve an aeseptic environment is directly
based on the pH of the must. Aeseptic levels are achieved with SO2
concentrations of .6 ppm in red musts & .8 ppm in white musts. To
achieve these concentrations, varying amounts of free sulphite need to
be added to the musts based on their pH.

Finished wines usually should have the following acid levels (expressed
as tartaric acid):

Fruit wines       0.60%  6.0g/L  6000ppm
Red grape wines   0.65%  6.5g/L  6500ppm
White grape wines 0.75%  7.5g/L  7500ppm
Sherry types      0.50%  5.0g/L  5000ppm

Common fruits will have the following acid levels:

Apple:        1.0%- 6.5%
Apricot:      6.0%-15.0%
Black Cherry: 3.5%- 7.0%
Elderberry:   6.0%-15.0%
Orange:       0.0%-35.0%
Peach:        3.0%-10.0%
Pear:         1.0%- 3.5%

1 ounce of acid blend will raise 5 imp. gal. by 0.13%. 1/4 ounce
calcium carbonate chalk or 1/3 ounce potassium carbonate chalk per
gallon will lower acid by 0.15%. Maximum recommended chalk is 0.5 ounce
calcium chalk per gallon to avoid a faint chalky taste. Potassium
bicarbonate produces better results with less taste then calcium
carbonate, and will work better with cold stabilization.

If your wine is really high in acid (VERY low pH), add some water or
mix with a wine with a VERY high pH. Alternately, add a 0.5%
sugar solution to your carboy about 1-2 days AFTER you have added
potassium sorbate to "stop" the fermentation. (0.5% = about 1 cup of
sugar/5 gal. of wine).

Here is an conversion table with tartaric to sulphuric equivalent:

ACID LEVEL (most useful range)

Tartaric Sulphuric
 (g/L)    (%)
  7.7     0.5
 15.3     1.0
 22.9     1.5
 30.6     2.0
 38.3     2.5
 45.9     3.0
 53.6     3.5
 61.2     4.0
 68.9     4.5
 76.5     5.0
 84.2     5.5
 91.9     6.0
 99.6     6.5
100.7     7.0

 

Continue to:

• prev: 27 Different Kinds Of Fermentation Used In Winemaking
• Index
• next: 29 Acid Balance: How Do I Relate Grams Per Litre Of Acid To Ph?

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