from the buffer capacity gave a similar result. The operation was even less effective when there was a high potassium level, and potassium bitartrate precipitated out when the tartaric acid was added.
Adding the maximum permitted dose of tartaric acid (1.50 g/hl) to second‐pressing must or wine was apparently more effective, as total acidity increased by 35% and pH decreased significantly (−0.14), producing a positive impact on wine stability and flavor. The effect on pH of acidifying wines shows the limitations of adding tartaric acid; there may also be problems with the secondary fermentation in bottle, sometimes resulting in “hard” wines with a metallic mouthfeel.
It would be possible to avoid these negative aspects of acidification by using L(−)lactic acid. This is listed as a food additive (E270) and meets the requirements of both the Food Chemicals Codex and the European Pharmacopoeia. Lactic acid is commonly used in the food and beverage industry, particularly as a substitute for citric acid in carbonated soft drinks and is even added to some South African wines.
Its advantages compared with tartaric acid are a pKa of 3.81 (tartaric acid: 3.01) and the fact that both its potassium and calcium salts are soluble. This enhances the acidification rate while minimizing the decrease in pH. Finally, lactic acid is microbiologically stable, unlike tartaric, malic, and citric acids. Until recently, one disadvantage of industrial lactic acid was a rather unpleasant odor, which justified its prohibition in winemaking. The lactic acid now produced by fermenting sugar industry residues with selected bacteria no longer has this odor.
TABLE 1.10 Composition of Chardonnay Wines After Tartrate Stabilization, Depending on the Time of Acidification (Addition to Must or to Wine After Malolactic Fermentation)
| Cuvée | Second pressing | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| 1995 | 1996 | 1996 | |||||||
| Control | Acidified must | Acidified wine | Control | Acidified must | Acidified wine | Control | Acidified must | Acidified wine | |
| pH | 3.06 | 2.97 | 2.97 | 3.06 | 2.99 | 2.97 | 3.18 | 3.04 | 3.00 |
| Total acidity (g/l, H2SO4) | 5.2 | 6.0 | 5.6 | 5.4 | 5.9 | 5.8 | 4.1 | 4.9 | 5.0 |
| Tartaric acid (g/l) | 3.6 | 4.0 | 4.3 | 4.4 | 5.2 | 5.0 | 3.4 | 4.6 | 4.8 |
| Malic acid (g/l) | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 |
| Lactic acid (g/l) | 4 | 4.3 | 4.4 | 4.2 | 4.1 | 4.1 | 3 | 3 | 2.7 |
| Total nitrogen (mg/l) | 274.7 | 221.9 | 271 | 251.6 | 280.3 | 289.8 | 245.9 | 250.4 | 254.4 |
| Amino acids (mg/l) | 1,051.4 | 703.7 | 1,322.6 | 1,254.2 | 1,422.7 | 1,471.7 | 1,177.5 | 1,350.4 | 1,145 |
| Potassium (mg/l) | 390 | 345 | 320 | 345 | 290 | 285 | 380 | 305 | 300 |
| Calcium (mg/l) | 71.5 | 90 | 79 | 60 | 64 | 61 | 50 | 55 | 48 |
| Buffer capacity (NaOH, H2O) | 48.1 | 56.6 | 56.2 | 50.3 | 55.5 | 56.9 | 42.4 | 49.1 | 47.7 |
| Buffer capacity (NaOH, EtOH 11% vol.) | 55.6 | 59.2 | 55.9 | 47.1 | 51.9 | 50.2 | 37.9 | 44.3 | 42 |
Cuvées were acidified with 1 g/l tartaric acid and second pressings with 1.5 g/l (Dartiguenave, 1998).
Current production quality, combined with low prices, should make it possible to allow experimentation in the near future, and perhaps, even a lifting of the current ban on the use of lactic acid in winemaking.
The fact that a wine has an acid–base buffer capacity also makes deacidification possible. The additives authorized for deacidifying wines are potassium bicarbonate (KHCO3) and calcium carbonate (CaCO3). They both form insoluble salts with tartaric acid, and the corresponding acidity is eliminated in the form of carbonic acid (H2CO3) that breaks down into CO2 and H2O. A comparison of the molecular weights of these two salts and the stoichiometry of the neutralization
