REDUCTION OF ACIDITY
WITH CALCIUM OR POTASSIUM CARBONATE
We have had some questions lately about high acid wines. This
season in the vineyard was very late and we had some problems with
higher acidity musts. This is some information from Presque Isle
Wine Cellars that is included in the package when you purchase acid
reducing chemicals.
1) Musts with total acidity (expressed as tartaric acid) above 1.2%
may produce wines too high in acidity for most people to enjoy. Such
musts will benefit from either the addition of water to dilute the
acidity (added as a 20% sugar solution before fermentation) or by
chemical reduction of acidity with calcium carbonate or potassium
bicarbonate (or potassium carbonate). Amelioration with sugar and
water is preferred where you have high flavor intensity (especially
with eastern varieties such as Concord, Catawba, Niagara and Delaware),
but are not concerned with body. The amount of reduction will be approximately
the percent of volume increase (ie. 1 gallon added to 9 gallons juice
= 1/9 or .11% reduction).
2) Some natural reduction in acidity occurs during fermentation when
about 10 to 25% of the malic acid is lost and during cold stabilization
when tartrates precipitate. Typically the reduction in acidity will
be 0.1 to 0.2% from these causes. There will be an even greater drop
if a malo lactic bacterial fermentation occurs when a reduction of
0.2 to 0.5% will normally result. Such a fermentation will be desirable
with most reds, but not with fresh, fruity whites.
3) Addition of 2.5 grams per gallon of calcium carbonate will reduce
acidity by 0.1 %. It reacts preferentially with tartaric acid rather
than malic acid. It also raises the pH fairly dramatically. For these
two reasons you will almost never be able to drop the acidity by more
than 0.4% by this method. You should try and keep the pH below 3.5
if at all possible. This material is best used in the fermenter or
before fermentation because the calcium ions will affect flavor for
some time after use and precipitation during cold stabilization is
more difficult than with the potassium salts (it will be more difficult
to commence and will continue for a much longer period because both
calcium tartrates and calcium malates are less soluble).
a) If you must drop acidity by more than about 0. 1 %, you should
add the calcium carbonate to a small fraction of your batch so that
you remove both malic and tartaric acids. After the reaction has completed
add this back to the main batch.
b) If you have both high acidity and high pH you may have to actually
add tartaric acid (to lower pH even though it increases acidity even
further) at a rate of up to 4.5 grams per gallon before you treat
with calcium carbonate. Afterwards, you must cold stabilize to reduce
the acidity.
4) Addition of 3.4 grams of potassium bicarbonate per gallon will
reduce acidity by 0.1 %. This material may be added immediately before
drinking and cold stabilizes more easily than a wine treated with
calcium carbonate, but has the disadvantage of raising the pH more.
A reduction of about 0.2% is a practical maximum. About 70 to 75%
of the acid reduction will occur immediately and the remainder during
cold stabilization. A salty or bitter taste will be evident in the
wine from the potassium ions when used at the upper levels. Potassium
Carbonate may also be used (2.4 grams per gallon will lower acidity
0. 1 %), but most of the research indicates a preference for using
potassium bicarbonate. You will get foaming when it is used because
of the CO, released.
5) It is possible to use a combination of acid reduction methods,
but remember that you cannot combine both calcium and potassium carbonate
or bicarbonate treatments without considering the effect of whichever
one you used first. In other words you cannot take a 0.4% reduction
with calcium carbonate and then a 0.2% reduction with potassium bicarbonate
use of one precludes the other.
PRESQUE ISLE WINE CELLARS
9440 BUFFALO ROAD
NORTH EAST, PA 16428
(814) 725 1314