De-acidification of Must
2. Double-salt de-acidification with "Neoanticid"
By this method tartaric and malic acids will reduce
in roughly equal parts as a so called double-salt, so it is clear why this
provides a substantially larger scope for de-acidification. Neoanticid is a
specially prepared 'chalk' with specific reaction properties which allow the
crystallizing of calcium malatartrate.
A special technique is necessary for carrying this out. For precipitation of the double-salt the pH value in the
must/juice has to be above 4.5. This is achieved by mixing the calculated weight of Neoanticid
with a portion of the must. The
portion will in this way be de-acidified totally and, after separation of
the resulting crystals, recombined with the portion which has not been
de-acidified. After mixing thoroughly the calculated acid content should be
reached. The procedure for treatment is described in detail below.
The manufacturers chart should be used to
determine the weight of Neo-anticid and the Partial Volume, according to the
initial acidity and desired final acidity.
In double-salt de-acidification the tartaric acid
content also limits the amount of de-acidification, but substantially more
scope for de-acidification is given than by using Kalk.
In order to reduce acidity by 1 g/l, 0.67 g/l of
Neoanticid is needed.
Required quantity of Neo-anticid (grams)= 0.67 x TV
x D
Partial Volume (litres) of must to be treated = TV x
D / TA
(plus % of TV if press-lees are included)
Maximum de-acidification possible in g/l = [TA x (WA
- FWA)]/[TA - WA] where:-
TV = total volume (litres) of must to be
treated
D = desired de-acidification in g/l
TA = total titratable acidity (expressed as tartaric
acid) in g/l
WA = tartaric acid content in g/l (typically 40% x
TA)
FWA = final tartaric acidity in g/l (has to be a minimum of 1.0 g/l)
The procedure for treatment:-
1. First it is necessary to rack off (or press out in
the case of red wine) the calculated Partial Volume of clear must to be
de-acidified.
With white wine it is usual to include the press-lees in the Partial
Volume, in which case a small % should be added to the calculated Partial Volume (to allow for solids that will not be
recovered).
Clear must is first racked into a receiving tank, leaving the Partial
Volume (including press lees) in the initial tank.
2. Mix the required weight of Neoanticid to a
paste with a little must and put in a third tank (or a vat), of capacity
at least 1.5 times the Partial Volume to be treated.
Then the Partial Volume of must is added very slowly
to the Neoanticid paste, mixing it
continually. In this way the freely emergent CO2 is driven off so that
stable pH conditions (above pH 4.5) are ensured.
3. After the CO2 release has been concluded,
complete separation of crystals should be carried out as soon as possible.
Usually, if left for 30 minutes the
crystals will have settled out sufficiently for a considerable amount of clear
must to be
racked off, the remainder should then be treated with Trub-ex.
4. As there is
very little
acid in the de-acidified portion it will oxidise quickly, so the de-acidified
portion should be added back to the non-de-acidified must
immediately.
If a suitable method of separation (eg. Trub-ex) is not available, then a simplified procedure can be
used: the de-acidified portion is mixed back into the non-de-acidified must without
the crystals being separated. After the crystals have been deposited the
relatively pure must which is left is carefully racked off. However,
especially where there are extreme acid values, there is a danger of calcium
tartrate backformation.
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