Acidity and De-acidification

Measurement of Acidity of Must or Wine:-

The acidity of must or wine can be measured by a test such as the Sulfacor.
The measurement gives the 'tartaric equivalent' acidity.
Regulations say that Table Wine shall have an acidity of at least 4.5 g/l.

Extent of De-acidification of Must or Wine:-

Regulation EC 1493/1999 Annex V.E is the main reference for de-acidification operations.

Wines are subject to a maximum limit of 1 g/l.

Must (and other products listed in E.1) may undergo unspecified 'partial deacidification' and it was decided some time ago that there is no limit on extent of deacidification for these (WSB interpretation, 822/97 Article 21 page 12).

Timing of De-acidification of Must or Wine:-

There is no definition in the EC Regulations of 'new wine still in fermentation' but this is seen as an incomplete operation (EC 1493/1999 Annex V.G Processes 'at the time when these products…are being turned into wine'). The permitted timing of the operation indicates that new wine may remain in fermentation for some months, as the deadline is given as 16 March.

According to EC Regulations a coarse de-acidification with any of the procedures set out below can be carried out on the must or young wine up to and including 15th March of the year following the harvest.
After 15th March an additional fine de-acidification is still allowed on the young wine, with all de-acidification procedures, "when the de-acidification of the product used for preparing the wine has proved to be insufficient". The fine de-acidification at this young wine stage is not related to the amount of de-acidification which has been carried out hitherto.
It is also possible to repeat the fine de-acidification several times providing that the permitted total de-acidification (of 1 g/l) is not exceeded. So after 15th March the wine can be de-acidified, for example, by 0.5 g/l twice.
In Germany this fine de-acidification is however expressly not allowed for table wine.

So 'Must deacidification' is permitted until clarification and stabilization takes place, or until 16 March. After this the EC Regulations on 'Wine deacidification' apply.

The recommended practice is only to de-acidify the must, and to do it before fermentation.

Allowed Procedures for De-acidification of Must or Wine:-

1. Simple de-acidification with "Kalk" (reduction of tartaric acid only).

2. Double-salt de-acidification with "Neoanticid" (simultaneous reduction of malic and tartaric acids).

3. Fine de-acidification with "Kalinat" (reduction of tartaric acid at the young wine stage).

4. Extended double-salt de-acidification with "Malicid" (unlimited scope in de-acidification with double salt de-acidification).

5. Biological de-acidification with "Bitec Vino" (particularly for red wines).

Otherwise with regard to the viticultural area and vine variety there are no limitations in the de-acidification procedures.

The choice of procedure to use depends on the following factors:-
- total acid content, and proportion of tartaric acid
- required amount of de-acidification
- required remaining tartaric acid content, and type of taste
- vine variety, and location of the vineyard
- date of de-acidification, whether must or wine, and date to be bottled.

Lowering of acidity arising from enrichment:-

When must is to be de-acidified prior to substantial enrichment, allowance should be made for the lowering of acidity due to the diluting effect (the volume of alcohol produced during fermentation) which will occur as a result of enrichment.

During fermentation between 45% and 48% of the weight of sugar is converted to alcohol, the rest is given off as carbon dioxide. Alcohol has a specific gravity of 0.7893 at 20°C.

So, 1000 ml of must with 11% vol natural alcohol (= 110 ml alcohol = 11 x 16.85 g/l sugar) after fermentation becomes 890 ml + (11 x 16.85 x 0.465 gm / 0.7893) = 1009.2 ml wine + CO2.

1000 ml of must with 10% vol natural alcohol (= 100 ml alcohol = 10 x 16.85 g/l sugar) + enrichment with 16.85 g/l sugar (= 1% vol alcohol = 10 ml), after fermentation becomes 900 ml + (11 x 16.85 x 0.465 gm / 0.7893) = 1009.2 ml wine + CO2.

and, 1000 ml of must with 7.5% natural alcohol (= 75 ml alcohol = 126.4 g/l sugar) + enrichment with 3.5 x 16.85 g/l sugar (= 3.5 % alcohol = 35 ml), after fermentation becomes 925 ml + (11 x 16.85 x 0.465 gm / 0.7893) = 1034.2 ml wine + CO2.

Thus, with 3.5 %vol enrichment the volume increases by 3.42% and consequently the acid will effectively be 'diluted' by the factor 1000/1034.2, reducing acidity by approximately 0.34% of the initial amount; 16 g/l reduces to 15.5 g/l.