by Jim Alexander October 13, 2002
The directions on my commonly used acid titration kit were wrong by omission so I did some research and summarized the results below. The kit said to dilute red wine to make the color change easier to detect. What it needed to say was: “Measure 15 ml of wine, add 15 ml of water. Titrate until permanent color change is obtained. TA is twice the number of ml of NaOH used because you diluted the acid by 50% before measuring.” The easiest units to use are grams per liter. If you measure 6 grams/liter TA and you want 8 grams/liter, simply multiply the number of liters times the 2 grams/liter you are short and add that much tartaric acid.
 | Adding 1 gram/liter of tartaric acid increases acid concentration by 1 gram/liter and decreases pH by 0.1.[1] |
| ¼ tsp of tartaric acid ~ 1.2 g, 1 tsp ~5 g, 1 TBLS ~15.6 g[2] |
| Adding malic or citric acid decreases pH by 0.08.[3] |
| Malolactic fermentation decreases TA by 1 to 2 grams/liter |
| Cold stabilization can also lower TA by up to 2 grams/liter |
Recommended ranges for red wines
Must
|
TA = 6 to 8 grams/liter (0.6-0.8% by weight)[4] |
|
pH = 3.6 to 3.3 (note that smaller pH means higher acidity) |
Wine
|
TA = 4 to 5.5 grams/liter (0.4-0.55% by weight) |
For reference
|
Water weighs 1 g/cm3 = 1 g/ml. This is how a gram was defined in the metric system. |
|
1 ml = 1*10-3 liter |
Acid concentration units explained
|
1 g/liter = 0.1% by definition |
|
1 g/liter = 1 g/1000 ml convert liters to ml |
Multiply both sides by 10
|
10 g/liter = 1 g/100 ml = 1% |
|
100 ml of water weighs 100 grams (100 ml * 1 g/ml = 100 g) |
|
1 gram of acid dissolved in 100 grams of water is 1% acid by weight. (1g/100g = 1%) |
Acid Titration
The easiest way:
|
15 ml of wine |
|
add 3 drops of phenolphthalein (color indicator) |
|
Titrate with 0.2 (1/5) Normal NaOH solution until permanent color change is obtained (pH=8.2). |
|
TA = ml of titrate solution required to obtain the permanent color change. |
|
Example: 6.5 ml = 6.5 grams/liter total acid. |
The hard way:
Dilute the 15 ml of red wine with the addition of 15 ml of water to make the color change more evident. TA = 2 * ml of titrate solution required to obtain the permanent color change.[5]
-
Winery Technology & Operations, Yair Margalit 1996 pg 52
-
Winery Technology & Operations, Yair Margalit 1996 pg 52
-
Ibid pg 50
- “Acidity: A Balancing Act”, Daniel Pambianchi, Winemaker, Spring 2001 Vol. 4, No. 1, pp 34-39.