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Optical Sorters Hasten Harvest

January 2011
by Thomas Ulrich
optical sorter
Grapes, stems and leaves are photographed as they enter the Delta Vistalys optical sorter.

After a week of unseasonably high temperatures, the sky darkened and cast a somber, uneven light across the crush pad at Clos Pegase winery in Napa Valley. Nearby, knots of field workers raced to pick clusters of Chardonnay and Cabernet Sauvignon as the Pacific jet stream poised to unleash a storm that would deliver a decisive conclusion to the 2010 harvest.

“A consistently cool growing season is a rare event in warm Calistoga,” said Richard Sowalsky, winemaker at Clos Pegase. “Everything was late. The mid- to late Chardonnay from our Carneros estate vineyard arrived at the same time as the early Cabernet from our Calistoga estate vineyards.”

With this year’s crop a month behind schedule, growers yearned for another week of warm weather to ripen the grapes completely. But Sowalsky and crew couldn’t wait for their luck or the weather to change. Time was running out. A storm that would douse local vineyards with nearly five inches of rain lurked off the Sonoma Coast.

A vintage known for its wet spring, cool summer and unpredictable harvest could be remembered as the year that French equipment manufacturers introduced U.S. winemakers to the optical sorter. At a cost of approximately $140 per ton, mechanically sorting grapes makes sense for many winemakers. It is a complicated decision that requires them to consider more than the cost of sorting grapes alone. Optical sorting accelerates the pace of work in the vineyard and the winery, its purpose to ensure that winemakers crush the highest quality fruit.

More with less
Before sunrise Oct. 22, Walsh Vineyards Management, based in Napa, Calif., delivered a Pellenc destemmer and optical sorter to the winery team at Clos Pegase. By noon, the machines and a six-person crew had separated and sorted 15 tons of grapes—three times as much fruit as a dozen crew members could have processed by hand.

With a sweeping motion, crew members raked clusters of grapes onto a pre-sorting table. They sifted through the clusters, pulling debris from a fast-moving, vibrating stream of grapes. An incline belt hopper loaded the clusters into interconnected polyurethane baskets that fed the grapes to a Pellenc “berry by berry” sorting system.

The destemmer detached berries from the stalks by moving clusters of grapes along a pair of vibrating inline berry separators. The fruit fell onto a notched roller sorting table that pushed the stems and other debris over the side of the machine and moved the berries into the optical sorter. A vibrating table carried them to a rope conveyor made up of 99 parallel cords that aligned what was left of the harvest for a final inspection.

The optical sorter photographed the berries and extraneous debris as they moved towards the ejection jets located at the end of the rope conveyor. The jets fired as seeds, jacks, raisins and imperfect berries cleared the end of the conveyor, hurtling them toward a waste bin. Momentum from the rope conveyor carried the unblemished grapes past a threshold and into a bin set aside for collecting the harvest.

“We did not have a day shift large enough to hand sort the amount of fruit we were receiving from the vineyards, especially while processing Chardonnay at the same time,” Sowalsky said. “Sorting 30 tons by hand alone could take three full days. With the destemmer and optical scanner we sorted 30 tons in a single day.”

With half as many crew members as he would have needed to sort the grapes by hand, Sowalsky assigned the other half of the sorting team the night shift to rack Chardonnay.

The optical sorter accelerated the pace of work in the field and at the winery, allowing a team half the size of the regular crew to destem and sort the harvest efficiently. Fewer workers at the sorting table meant more team members to tackle work inside the winery during the busiest time of year.




Raising the bar
Thirty-five miles south in Sonoma, Anne Dempsey, lead associate winemaker at Gundlach Bundschu, unloaded an empty receiving bin near a Delta Vistalys optical sorter. Like Richard Sowalsky from Clos Pegase, Dempsey faced a challenging vintage equipped with one of the first optical grape sorters in the county. And like the Pellenc optical sorter, the Delta Vistalys determined every grape that Dempsey pressed into estate Cabernet to ensure that she selected unblemished grapes instead of debris that can affect the taste, body, color and aroma of the wine.

“We can make top-notch Cabernet sorting 40 tons of grapes a day and still raise quality,” Dempsey said. For her, the optical sorter is a tool to make the winery’s high-end wines even better.

“Leaves are the biggest concern with hand sorting,” she added, “but I can be as selective as I want with an optical sorter.”

First she must adjust the machine.

Manufactured by Bucher Vaslin, the Delta Vistalys optical sorter selects grapes much like the Pellenc optical sorter. Both machines distinguish whole grapes from stems and leaves, then pass the grapes across a row of ejection jets to separate the fruit from any extraneous debris.

The challenge is to set the optical sorter to discard the jacks, raisins, seeds, stems and unripe fruit in favor of the grapes Dempsey and Sowalsky want to make into fine wine. Both machines permit the winemaker to select fruit by color, size and shape.

To adjust the machine, the winemaker defines what to throw away and what to keep. With a digital camera that can be programmed to discern the difference between wanted and unwanted berries, the sorter whisks the selected grapes into one bin and the unsuitable grapes and debris into another.

“It’s a balance between good grapes falling into the waste bin and jacks, stems, seeds and raisins from falling into the fruit bin,” she said.

For each load of grapes, the winemaker evaluates the material from the receiving bins for the grapes and the debris, then resets the machine to refine the process.

More challenging than peas
Scientists have evaluated frozen vegetables and coffee beans with optical sorters for years. Bucher Vaslin and Pellenc developed optical sorters for the wine industry in France, where they launched the equipment in 2008. A grape fresh from the harvest can pose challenges a pea does not. Technicians need to calibrate the Pellenc and Bucher Vaslin optical sorters to measure the difference between a blemished and unblemished grapes as well as whole berries vs. raisins.

But reports from the winemakers testing the technology in the U.S. are favorable.

Following a challenging growing season and unpredictable weather events, winemakers Sowalsky and Dempsey accelerated the harvest by sorting grapes at least three times faster with a machine than by hand. And they discovered that optically sorted fruit can elevate the quality of their wines.

“During the peak of the 2010 harvest,” Sowalsky said, “our workforce was stretched thin. The optical sorter was on par with a discerning eye, allowing us to sort much more quickly and with a much smaller crew than if we sorted by hand.”

“We were able to accelerate the harvest and improve quality,” Dempsey added. “Hand-harvested and machine-sorted grapes are producing amazing wines.”

Thomas Ulrich has written news, features and advertising copy for Time magazine, the Christian Science Monitor and The New York Times. He was a senior writer for Hewlett-Packard for many years and a contributing editor for Sun Microsystems. He teaches journalism at San Jose State University.

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