WRE Sensory Session: Jacks & Stems
March 22, 2023
Stone Tower Winery
Unsorted fruit at Blenheim Vineyards. Photo credit: Kirsty Harmon
Stems can be a very controversial topic. Some winemakers hate even the smallest jack in the red wine ferments while others intentionally include whole cluster fruit, stems and all. Though destemmers include technology to reduce MOG, many wineries still spend precious time and human resources to painstakingly remove jacks for their higher end wines. Is it worth the time and (labor) cost to sort out jacks post destemming? Is it beneficial to include stems for some varieties?
In 2023, three WRE experiments examined questions related to jacks and stems:
The first was an experiment done by Shane McManigle from Doukenie Winery exploring the effects of whole cluster inclusion in Syrah. The purpose of this experiment was to determine if whole cluster inclusion would increase Syrah varietal character and weight in Doukenie Syrah. There were three treatment levels with 0, 25% and 50% whole cluster inclusion fermented with destemmed fruit. Increased whole cluster inclusion led to decreased alcohol and color and increased pH and acetic acid. Wines produced from 100% destemmed fruit scored the highest for fruit character, indicating dark/black/dried fruit vs. bright/red/fresh fruit character in wines produced with whole cluster inclusion.
We then turned our attention to the question of post-destemming sorting with experiments from Doug Fabbioli (Fabbioli Cellars) and Kirsty Harmon (Blenheim Vineyards). Post-destemming sorting of jack stems as a way to limit green character and harsh stem tannins is a common practice in Virginia wineries. However, post-destemming sorting is labor intensive and time consuming. The purpose of these experiments was to determine if the time and effort spent sorting jack stems made a perceptible difference in overall wine quality. Experiments at both wineries were conducted using both Cabernet Franc and Petit Verdot. For each variety, one TBin of fruit was fermented from grapes that were sorted post-destemming while a second TBin of fruit was fermented from grapes that were not sorted.
At Fabbioli, general wine chemistry was very similar between treatments for both varieties. In each, the unsorted fruit produced wine that had slightly higher tannins. The Cabernet Franc wines were not significantly different in a triangle test. The Petit Verdot wines were distinguishable in a triangle test, however there were no differences in sensory scores for fruit intensity, fruit character, herbaceous/green character, bitterness or astringency. In this experiment sorting took approximately 30 minutes per bin, with 4-6 people working the sorting line.
At Blenheim, there was a slight increase in pH, acetic acid, and tannin but no change in methoxypyrazine in the finished wine when Cabernet Franc grapes were not sorted. The wines were not significantly different in a triangle test. Those that could tell the difference between the wines rated the wine made from sorted fruit as having higher astringency while there were no differences in bitterness ratings. The wine made from unsorted Petit Verdot also had higher pH than the sorted treatment, with no differences in the other chemical measures. The wines were not significantly different in a triangle test. Those that could tell the difference between the wines rated the wine made from sorted fruit as having higher fruit intensity with no other differences in descriptors. In this experiment, sorting fruit came at the cost of considerably slower destemmer speed (2 tons/hour vs. 5 tons/hour) as well as labor (3-5 people at the sorting table).