De-acidification with Kalk (Calcium carbonate, chalk) is used against a high tartaric acid content, mainly on the must although it can also be utilized on young wine. Since, with this kind of de-acidification, only the tartaric acid is reduced the limiting factor is the proportion of tartaric acid in relation to the total acid. The proportion of tartaric acid varies considerably according to climatic conditions, different sites and different vine varieties; information about this should be obtained from laboratory analysis.

For reasons of taste (tartaric acid tastes 'less acidic' than malic acid) a tartaric acid content of at least 1 g/l must remain.

In order to lose 1 g/l tartaric acid 0.67 g/l of Kalk is needed:

Required quantity of Kalk (grams) = 0.67 x D

Maximum de-acidification possible in g/l = (TA x %partWA)/100 - FWA

where:-

D = desired de-acidification in g/l

TA = total titratable acidity (expressed as tartaric acid) in g/l

WA = tartaric acid in g/l (typically 40%)

FWA = final tartaric acidity in g/l (minimum 1.0)

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