Page 11 - Grapevine NovDec 2021
P. 11

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


               877-892-5332                 The Grapevine • November - December 2021                             Page 9





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