Harvest: Time To Crush It -- Part 2

In part two of Grant’s harvest blog series, we rejoin our grapes in the winery…

Step 2. Grape crushing time

The grapes waiting outside Winery SF (with the Bay Bridge in the background)

The grapes waiting outside Winery SF (with the Bay Bridge in the background)

From the sorting table, the grapes run straight into the crusher. Stems are removed during crushing, either by hand or by a fancy modern machine called a ‘crusher destemmer’ that, as you might imagine, performs both functions at the same time. The grape skins are smashed, unleashing the sweet juice contained within. Large wineries will crush into big stainless steel tanks, while smaller lots are fermented in one ton square bins.

Grant and his grapes.  The winery is at max capacity this week, full of those 1 ton bins of grapes.  

Grant and his grapes.  The winery is at max capacity this week, full of those 1 ton bins of grapes.  

The combination of the juice, skins, and seeds is known as the must. This cocktail of solids and liquids starts out cold, light colored and sweet. The fleshy pulp of the grape is actually clear in color, as is the juice of a freshly pressed grape. All the color of the wine is pulled from the skins over the next two to three weeks after crushing.

Grapes beginning fermenting, transforming sugars into alcohol and CO2. 

Grapes beginning fermenting, transforming sugars into alcohol and CO2. 

Winemakers often choose to wait a day or two prior to inoculating, or adding yeast into the must. This process, called cold soaking, diversifies the extraction of color and flavor. By letting the juice remain on the skins at a cool temperature, a softer, less intense extraction occurs. This process will also extend the total maceration time, or the time that the skins are in contact with the juice.

Since there are wild yeasts on the skins of grapes and in the air, yeast inoculation is not mandatory to make wine. Wild yeast fermentations can add complexity to a wine and lead to flavor variations from year to year. However, natural fermentations can be prone to higher levels of volatile acidity, the precursor to vinegar.

The addition of certain types of yeast to the must can insure a steadier fermentation and minimize the risk of spoilage. Much of the risk involved in wild yeast fermentations depends on the sanitation of the facility and if the winemaker is willing to roll the dice on the wild yeast being strong enough to survive the fermentation. When we decide whether to inoculate the must, it all boils down to one simple question: are we feeling lucky?

In the third and final part of the series, we’ll cover what happens during fermentation, and how we finish the crush process, and what we do once it’s all over.