Page 11 - Grapevine NovDec 2021

In The Winery

on the crush pad there is often a significant quan- be used. Wines were often chilled for two to three
tity of tartaric acid and potassium available in the weeks at 27 degrees F and allowed to drop their
grapes to result in instability. Furthering the com- tartrates during this time. This process was often
plication is the fact that the crystals are encouraged successful but it did have its failures due to com-
out of solution, forming further precipitation, in the plexing agents that prevented the tartrates from
presence of alcohol. The fact that the winemakers forming.
have completed a successful fermentation will only
force more of the crystals to precipitate. The pro- Contact Seeding
cesses to remove these crystals are largely a time
temperature relationship. Over time, and at low Perhaps contact seeding is more widely used
temperatures, most to all of the tartrates will form today especially with wines that are blended late
and fall out of solution. in the winemaking process or for getting young-
er wines ready for bottling sooner. This process
3.65 pH Bifurcation * rarely fails and it does allow acid additions to be
made even hours prior to using this process. Some
A very interesting phenomenon does exist with winemakers claim this action can be intrusive and
tartrate stabilization in wine made from grapes that beyond gentle processing; yet, others would have it
all winemakers should understand. (This may not no other way.
apply to fruit wines) For a wine above a pH of 3.65,
one should expect the pH to rise as tartrates form Procedure
and fall out of solution. For a wine below a pH of
3.65, the pH will drop to a lower pH value. The For those interesting in contact seeding, a proce-
shift, of the pH, is usually about 0.06 pH units but dure follows. One must have an adequate chilling
it can go as high as 0.19 pH units. This knowledge system, mixer, tanks that have little temperature
can be used, factored into and forecasted by the stratification and a filtration system that can fil-
winemakers’ ultimate plans for a certain wine’s ter reasonably rapidly. A properly sized plate and
final pH. frame filter is sufficient for most winemakers while
using a pore size pad of roughly 7 microns. It is
Tartaric acid and pH relationship assumed the wine is clean enough to go through
the filter pads without clogging and at a rate that
Noting the example above, one must understand will not allow the wine to warm too much poten-
another relationship. In both examples, whether tially redisolving the tartrates previously formed
the pH rises or lowers during tartrate stabilization, during the filtration process. It is best to always
the tartaric acid level will decrease in the wine as check a wine first to make sure the wine is unstable
it has formed in a salt and precipitated. The tar- before proceeding with this process. One may be
taric acid has formed with potassium and become able to eliminate this process if the wine is already
insoluble at that temperature during that time. If stable.
the wine were to warm, however, the salt could
re-soluablize negating the above statement. 1.Chill the wine in need of stabilization to approx-
imately 27 degrees F or potentially lower if the
Temperature and Potassium alcohol level is high enough and if greater stability
Bitartrate Formation is desired. The wine will be stable at the seeding
temperature of the wine at seeding so this tem-
As noted previously, the precipitation is largely perature reduction step is critical. (In the unusual
influenced by a time temperature relationship. case that the wine is below 8% alcohol, one would
Wine allowed to store over long periods of time will not want to chill the wine this cold.)
most likely achieve stability and it can be bottled.
With the advancement of sophisticated chilling 2.Start to mix the wine with a Guth or Keisel style
systems in the wine industry, another process can tank mixer after the desired temperature has been

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