Winemakers can thank Lucille Ball for glamorizing the crush during her iconic grape-stomping escapade in I Love Lucy. And while manually pressing grapes has fallen out of fashion in the tech age, there are a myriad of tricks of the trade I discovered last month during a trip to Napa. As John Hendrick, a home winemaker in St. Helena, knelt between rows of Merlot and Cabernet Franc, he taught me a few things about viticulture. Hendrick invites volunteers to pick grapes on his one-third of an acre lot, as do a handful of vineyards.
With more than 3,500 wineries in California harvesting 4 million tons of grapes annually, there is ample opportunity to participate. Here are a few insights, and a list of places where you can experience the harvest yourself.
1. The time of day you pick is just as important as the time of year
You may know that August, September and October are the best months to harvest but did you know the time of day is just as important? In the dead of night, tractor-mounted lights flick on and field hands load baskets full of grapes in a practice that is increasingly common in California and throughout the world. Harvesting at night saves money (no need to cool grapes before crushing), is easier on the workers and ensures a stable sugar level in the grapes, something that fluctuates when the temperature rises.
2. To manipulate sugars and acid, grapes are picked early or left on the vine
Collecting grapes takes several months because the optimum ripeness varies from varietal to varietal. In California, white grapes like Sauvignon Blanc are picked first because winemakers look for lower sugar to acid ratios to give those wines a crisp, almost tart taste. Red grapes are picked later and grapes for dessert wine, like “late harvest” Riesling, are left on the vine even longer so the fruit continues to ripen, i.e. produces more sugar, resulting in a sweeter wine.
3. Moldy grapes make some of the best wine
To produce sweet wine, vintners rely on a fungus called Botrytis cinerea or noble rot, which shrivels and decays the grapes creating two desirable traits: more sugar and a distinctive taste. Noble rot dries out the grapes making the sugar to water content higher which leads to a sweeter wine. The fungus also has an aromatic compound called phenylacetaldehyde that gives wine a “honey” or “beeswax” flavor. Wineries like Beringer can now create botrytis-affected wine entirely in the laboratory by adding spores to trays full of grapes in temperature controlled rooms.
4. Grapes are sometimes fermented with wild yeast from the field
While yeast is the essential component that converts grape juice into wine, not all yeast is added in the barrel. Most people are familiar with cultured yeast which is intentionally added, but wild yeast can play a role too. This naturally occurring yeast, often called bloom or blush, coats the grapes in the field and starts the fermentation process almost immediately after the fruit is crushed. It’s widely used among home winemakers but less common in wineries since full fermentation is rare unless cultured yeast is also added.
5. High-tech optical sorters separate grapes with surprising accuracy
And that’s a good thing. Hand-sorting through a million tons of grapes to check for mold and other imperfections is laborious and time consuming, so wineries have employed optical sorters that discard exactly what the winemaker deems undesirable. After grapes are de-stemmed and placed on a conveyer belt, the machines use ejection jets to discard unwanted berries. The devices take digital photos and know exactly which grapes to discard based on information the winemaker has entered about the color, size and shape of the grape. Using targeted air blasts, the sorter sends selected grapes into one bin and unsuitable grapes and debris into another. Wineries like Silverado Vineyards and Clos Pegase have adopted the technology, which more than doubles the rate of production.
6. The romanticized grape stomp is a thing of the past
Lucy would be disappointed at her prospects today, as most human grape-stompers have been replaced by de-stemmers/crushers. Hendrick uses an enamel de-stemmer/crusher from a fellow winemaker with an oversized “corkscrew” to shoot out the stems and let the crushed grapes fall into a bucket below. Sidenote: if you leave the stems on during fermentation you get Grappa, a distilled wine made from crushed grapes, seeds, skins and stems that is popular in Italy and Spain.
7. The sugar content in wine is evident before it’s barreled
Brix, a measurement of the amount of sugar in grape juice, is calculated after de-stemming using a refractometer. One brix equals one gram of sugar per 100 grams of liquid, which shows up in the refractometer as a shadow inside the instrument. Winemakers dip the device into the juice hoping for a reading between 24 to 27, which predicts an alcohol content between 12-15%.
8. It’s not the grapes that determine the color, it’s the skin
Red wine obviously comes from red grapes but can white wine also come from red grapes? The answer—sort of. To get the red color, winemakers leave the skins on red grapes during fermentation. To get white wine from red grapes, vintners remove the skins from red grapes before processing. Technically, the resulting wine is a rosé but is often marketed, like White Merlot, as white wine. White Zinfandel has also gained traction but is something different altogether.
9. Fermentation happens in a fortnight
Once the juice is sealed in oak barrels or housed in stainless steel tanks, the yeast gets straight to work. Fermentation only takes two weeks but wine is left to age. During the aging process wine takes on distinct characteristics of the container and develops a unique flavor profile. Whether it’s aged for two years or ten, no bottle of wine is the same, which is what wine enthusiasts love about the surprise poured into each glass.
JOIN THE HARVEST
Here are a few wineries that welcome volunteers: