Labo VinCorrecting the acidity
The acidity of juices is rarely well-balanced (table of fruit juices acidity). A good wine must have an ideal acidity, tally with its class and the drinker taste, but also a minimal acidity is necessary to insure the wine keeping. It is therefore often necessary to correct the acidity in order to reach this ideal value.
A scantily acidic juice will be easily corrected by adding a suitable amount of acid.
- An acid mixture [ Using an acid mixture for the sap correction leads to more harmonious wines than a unique acid, because each acid acts on the yeast metabolism in a special way.
We recommend this mixture:
- tartaric acid: 551 g
- malic acid: 248 g
- citric acid: 152 g
- succinic acid: 49 g
1 g of this mixture is equivalent to 1 g tartaric, which is our acid unit. ] is more conducive to the shapely wine development than one acid alone.
- The correction can also be made by mixing with another juice having a higher acidity, but obviously this mixture will impart a different taste to the wine.
An excessive acidity can be reduced in several ways:
- Diluting the juice with water or another sparsely acidic juice (acidity table).
- Adding a neutralizing chemical:
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A reasonable amount of calcium carbonate can be added. No more than 6 g/L in order to avoid a chalk savour. Adding 0.6 g/L CaCO3 decreases the acidity by 1 g/L Eq. tartaric acid. Dilute the powder in a small amount of juice before adding to the carboy. Mix well; some CO2 will escape and insoluble calcium salts of the neutralized acids will settle in the bottom. After a few hours rest, rack the juice. At this moment the juice has not to be necessarily perfectly clear.
CaCO3 can also be used to eliminate the toxic oxalic acid present in some materials (especially unripe rhubarb). 1-2 g/L will be used. - You can also use a reasonable amount of potassium carbonate (K2CO3, MM = 138 ; 1 Eq = 69.1 g; 0.92 g neutralizes 1 g Eq. tartaric acid) or potassium hydroxide (KOH, MM = 56 ; 1 Eq = 56 g; 0.75 g = 1 g Eq. tartaric acid). Be careful, an excess can give the wine a salt savour because potassium ions are not eliminated from the wine (a moderate amount is not noxious; there is yet some potassium ions naturally in the juices). Do not outrun 3-4 g/L.
- It is possible to decrease specifically the amount of tartaric acid by adding potassium tartarate. The resulting potassium bitartarate will settle (one can often see crystals in the bottom of wine bottles or clogged on the corks). 1.5 g potassium tartarate will eliminate 1 g tartaric acid.
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A reasonable amount of calcium carbonate can be added. No more than 6 g/L in order to avoid a chalk savour. Adding 0.6 g/L CaCO3 decreases the acidity by 1 g/L Eq. tartaric acid. Dilute the powder in a small amount of juice before adding to the carboy. Mix well; some CO2 will escape and insoluble calcium salts of the neutralized acids will settle in the bottom. After a few hours rest, rack the juice. At this moment the juice has not to be necessarily perfectly clear.
Important: during fermentation, the acidity decreases by 1-3g/L. It must be taken into account when calculating the correction.