How Mechanical Harvesting Impacts Wine Quality

As labor becomes even scarcer, even ultra-premium wineries are expected to turn to mechanical harvesters. Will wine quality suffer?

The stereotypical image of a wine harvest is timeless: a legion of workers making their way down the vines, removing bunches of grapes one by one, and then carrying them in a basket to a waiting vehicle. But in many parts of the world that scene is a quaint piece of history; in California, for example, 90 percent of grapes are harvested by machine. 

With labor being harder and harder to come by, machine harvesting is only expected to become more common worldwide, but that shouldn’t be cause for alarm for lovers of quality wine. Advancements in technology, for example, are helping producers harvest more high-quality grapes without the need for a large, seasonal workforce.

SevenFifty Daily spoke with researchers and winemakers working around the globe to learn more about how mechanical harvesters have evolved and how they impact grape quality, the resulting wine, and the operational requirements of a busy harvest season.

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Machine Harvesters Then and Now

Mechanical harvesters work by shaking berries loose from the vine. The machine, which resembles a tall tractor, drives over each row in the vineyard, straddling the vines. It then uses rods to gently shake the vines. The berries fall onto a conveyor belt, which deposits the grapes into a collecting bin for eventual transport to the winery. 

Marty Spate, the head winemaker at Riboli Family Wines in Paso Robles, California, has been working with machine harvesters since 2005. “I remember them being very rough on the vines,” he says, noting that they resulted in a lot of broken twigs and sticks making their way into the hopper. But perhaps more importantly, “There would be a lot of broken berries. When you’re processing [the grapes] at the winery, you’d tip the gondola up and get a waterfall of grape juice pouring into the hopper.” For white wines, that leaked juice could lead to oxidation issues or unwanted color extraction. 

In 2014, Spate had the opportunity to work with a new line of machine harvesters made by the French firm, Pellenc, which many credit with refining the modern harvester into what it is today. “I’ve been working with these new machines for 11 years now and I haven’t seen any wood coming through,” says Spate. There’s far fewer broken berries and less juice, too, though Spate says pink grapes destined for white wine, like Pinot Gris, or reds harvested for rosé, are still best harvested by hand to control the levels of color extraction.

“It was a very primitive thing,” says Jonathan Walters, the vice president of vineyard and winemaking operations at Brassfield Wine Estate in Lake County, California, of the older machines, “but now these machines have changed dramatically. We have a destemmer on the machine now, so we leave all the stems and leaves in the vineyard, so they compost in the vineyard.” Walters also points out how delicate the machines are now. “Previously, it was just full throttle, but now you can dial in everything: frequency, pitch, and how hard it hits the vines. Some machines even include optical sorting of the fruit before it ever reaches the winery.”

“What we’re receiving into the winery is akin to what you’d see in the grocery store when you go buy your little clamshell of blueberries,” Spate says. “You get what I would consider a premium, luxury-tier product.”

How Mechanical Harvesters Impact Grapes and Vines

Much of the technology upgrades have focused on automating the sorting process, replacing the human eye with technological ones, but the contrast between the human hand and the mechanical rustle of the harvester does affect some grape varieties, though not always in a negative way. 

“A lot of studies show that [mechanically harvested] Sauvignon Blanc berries release more aromatic precursors and enzymes,” says Dr. Kristy Sun, an associate professor of enology at California State University, Fresno. “New Zealand Sauvignon Blanc is famous for its passion fruit aroma; if you do mechanical harvesting you actually help bring that out.” One study found the levels of the thiols responsible for the aroma could be from five to 10 times higher in mechanically harvested Sauvignon Blanc grapes. While the actual cause of this increase has yet to be determined, some studies suggest that increased enzyme activity in the berries is responsible.

Some grapes may be less suitable for mechanical harvesting. Sun speculates that Pinot Noir’s thin skins make it more challenging to harvest it by machine. At Torre Zambra in Abruzzo, Italy, owner Federico De Cerchio says that mechanical harvesting’s potential in the region hinges in part on the thick skin of indigenous grapes such as Pecorino, Trebbiano, and Montepulciano.

Little research has been conducted to measure the impact of mechanical harvesting on the vines themselves. In an early study from 1977, 75 percent of vineyard owners reported no damage. Some reported defoliation or the loss of canes or spurs that could impact yield in future years, but nothing was conclusive. 

Walters believes there could be some impact on vine ageability. “Sauvignon Blanc is very sensitive to wood disease,” he says. “I do believe that the machines are imparting some vectors for disease, because there are cuts and scars on the plants.” He estimates that vines that might otherwise live 40 years or more, may not last beyond 30 years when harvested by machines over their lifetimes.

How Mechanical Harvesters Impact Vineyard Operations

Long associated with cheap, low-end wines, there’s no denying that machine harvesters can save growers a substantial amount of money. “We can machine pick for between $50 and $100 per acre,” says Walters. “Hand picking can be as much as $200 to $500 per ton.” Averaging five tons per acre, that’s a huge savings.

Far fewer people are required as well; machine harvesters only require a single driver, as opposed to the many pickers and tractor drivers one might need for hand harvesting. There’s also labor savings at the winery, as hand sorting can be replaced by the machine’s onboard destemmer and sorter.

With labor in high demand, more and more wineries are exploring this option. “In the coming years, we don’t know who’s going to pick the grapes; it’s getting harder and harder,” De Cerchio says. “And if we have to let the grapes die in the vineyard at the end of November, no one’s going to be happy. So, I think that for the future, we have to [rip up our pergolas], plant our rows, and start to mechanize, especially for whites.”

In Washington State, Sagemoor Vineyards manages 1,200 acres of vines and supplies over 100 wineries with grapes. According to brand ambassador Kent Waliser, the oxidation and sorting problem used to mean that machine-harvested grapes were only suitable for wineries very close to the vineyard. 

“Once we got that new machine technology, we could bring the fermenting tubs out into the vineyard and run the fruit directly into them,” says Waliser. “The wineries could then take the tubs back to the winery and ferment directly in them,” which saved multiple steps and solved logistical challenges. “Now, we pick the fruit at night with a machine. The winery can pick up the fruit at seven or eight o’clock in the morning, [drive] one or two hours back to the winery, put it in their fermenting rooms, and that’s it.”

Despite the upfront investment—prices are in the hundreds of thousands of dollars—machine harvesters are only becoming more popular. Labor problemsaren’t going away, and being able to pick quickly, even at night, is vital, especially where fires could threaten an entire vintage. But ultimately, this option only works because of the quality that ends up in the bottle. 

“If you told me back in 2005, ‘Marty, someday you’re going to be making $100 bottles of wine with machine-harvested fruit,’ I would have laughed at you,” says Spate. “But this is a very, very different world we live in now.”