I recently had the pleasure and privilege to volunteer at Vin 312, a family-owned winery on the North side of Chicago. They recently received this year’s freshly harvested Sangiovese grapes! When grapes come in, you must move fast in order to process them and get them ready for fermentation. The urgency is critical to ensure the grapes spend as little time as possible in contact with oxygen, which can make the grapes go bad from over-exposure and unwanted levels of oxidation. So the race was on!
Grape Reception
These Sangiovese grape clusters were hand-picked and loaded into bins suitable for shipment. Grapes usually ship around 35° F to retain freshness and prevent spoilage. In addition, warm temperatures can cause natural fermentation to begin from the presence of ambient (local) yeast already on the grape skins.
Note: Grapes left in warm temperatures will begin to naturally ferment on their own.
We opened the large bins one by one. Brrr, the grapes were still so cold I was sure my hands were frozen! Each cluster was in-tact and still attached to the grape stems. Some grapes were big and juicy, others were shriveled and raisined. Raisined grapes naturally lost some of their water on the vine and typically have higher levels of sugar concentration.
Sorting
We then sorted the grapes and removed non-grape “stuff.” In the interest of time, we quickly took out all leaves, twigs, and other interesting vegetation that somehow got included between clusters. We also removed grapes that had any mold or looked to be damaged in any way. The goal was to only move the healthy grapes along to the crusher. It took about 20 minutes to work through each bin and remove all the unwanted debris.
Destemming & Crushing
Once the debris was removed, we ushered the full clusters into a destemming and crushing device. The clusters fell into the crusher, the stems were removed and the grapes were split open, creating “free run” juice (considered to be the purest form of grape juice).
The stems and other debris exited the back-end of the crusher.
Cold-Soak
A tube connected to the crusher channeled the grape juice into an awaiting fermentation tank. The grapes underwent a cold maceration, or “cold-soak” for several days before fermentation in order to maximize color and flavor complexity. This process takes place at temperatures too cold for fermentation to begin. In order for fermentation to kick off, the tank temperatures are raised to activate the yeast.
Fermentation
During fermentation, yeasts convert the juice sugars into alcohol. Wild (ambient) yeasts exist naturally on grape skins, stems, and even in the winery itself. A winemaker can choose to use these naturally-present yeasts to complete the fermentation process, or add yeast to the juice (most common). The grape juice temperature must be adjusted to the right setting in order for yeast to begin and continue their job.
Over the course of several weeks, the yeasts consume the grape juice sugar and replace it with Carbon Dioxide and Ethanol (alcohol). Once the yeasts consume all the sugar, they die and are filtered out of the wine. However, if the winemaker were to remove the yeasts before all the sugars were consumed, the wine would remain sweet with lower levels of alcohol.
Don’t forget to order your bottles from Vin 312!
Cheers!
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Your discussion of wine making, with pictures for sorting and crushing is quite informative. Also the fermentation process is central to getting the wine right