What is Whole Cluster Fermentation? This refers to the practice of fermenting entire bunches of grapes, stems and all. Typically, our grapes go through a destemmer, a machine that knocks the berries off the stems. In the process, many of the berries split and begin to release juice immediately. When we bypass that step, the fruit stays intact longer, releasing the sugar available to the yeast more slowly. This results in fermentations that take longer to complete, at much lower temperatures. The shift in fermentation kinetics, along with the presence of the stem has an impact on aroma, flavor, and structure of the wine. Are these features beneficial to the overall quality? How much whole cluster is the ideal amount, if any? Will our ideas about this change as the wine ages? With the vintage? These are all questions we hope to answer through our whole cluster series.
In 2014, we harvested five tons of Pinot Noir from the same part of the vineyard, and separated the fruit into five fermenters. We added a whole cluster layer in four of these vats, 25%, 50%, 75%, and 100%. The fifth bin was all destemmed. We proceeded with our typical fermentation management protocols, with pumpovers and punch downs twice daily, and pressing at dryness. The wines were aged in older French oak barrels and bottled the winter of 2016.
We observed differences in the fermentation kinetics almost immediately. The vats with higher percentages of whole cluster fermented at lower temperatures:
This also correlates with fermentation rate, as indicated by the rate of sugar depletion.
It seems that utilizing whole cluster fermentation as a technique results in a slower fermentation with lower temperatures. Cool, right?
We found that the chemistry of the finished wines was varied, although this could be due to differences in ripeness levels in the field, and/or clonal differences throughout the block. It is important to note that each vintage is unique, so for us to learn anything meaningful from this exercise, we will need to repeat the experiment over multiple vintages in varying conditions.
Our 2014 whole cluster Pinot Noir set includes one bottle each of the experimental wines, and the 2014 Pinot Noir Yamhill-Carlton, for a total of six bottles. This collection is a lovely gift, and fun to share at a dinner party or with a group of friends.