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Sorting Table Ensures Only Berries of Desired Ripeness Selected

by Mike Dunne
February 14, 2020

Merlot grapes being conveyed from bin to bath in the first step of using the densimetric sorting table.
Photos by Mike Dunne
Herve Lhuillier, owner/winemaker of Chateau Fleur Haut Gaussens in Bordeaux, center, explains the workings of his densimetric sorting table.

 

In their ceaseless quest to work with only the most pristine grapes, winemakers are turning to a high-tech bath intended to assure them that the fruit they are about to transform into wine is at pitch-perfect ripeness.

Meet the “densimetric sorting table,” a Rube Goldberg-like machine with conveyor belts, funnels and chutes to transport freshly harvested grapes through a hopper of water treated with a sugar solution and calibrated so only fruit of a desired ripeness sinks and then is retrieved for fermentation. Picture the slides, tubes, pipes and pools of a water park, only on a smaller scale.

Grapes lacking the requisite density – or ripeness – float, along with leaves, insects, twigs and similar “material other than grapes,” which winemakers call MOG. They then are swept off and discarded, like debris skimmed from atop the water of a swimming pool.

Herve Lhuillier, owner/winemaker of Chateau Fleur Haut Gaussens at Verac in Bordeaux, is an early adapter and persuasive proponent of the technique. He jumped about his vibrating and churning Bucher Vaslin Delta Densilys densimetric sorting table as he ran samples of Merlot through the bath during this past fall’s harvest.

He first rented it for a trial run during the 2018 vintage. Encouraged by the results, he soon paid 32,000 euros for his own machine, the equivalent of about $35,000. “I could have saved some money by buying it this year,” he remarked, noting that the price last fall had been reduced to 28,000 euros (about $31,000).

The adjustment of the bath, which varies by grape variety, by the nature of the vintage and by the precise alcohol content he seeks in his wines, has been the most challenging aspect in learning how to take best advantage of the table, but after two unsuccessful runs at the outset he now feels he has a handle on the matter.

The composition of the bath involves using a formula to determine how much sugar to add to the water in the hopper to assure only berries with the desired degree of ripeness sink to the bottom, where a belt rescues them and carries them to fermentation tank or barrel.

Lhuillier sees his use of the table as an extension of his commitment to modernizing winemaking in Bordeaux, which he regards as too often “old and stuffy.” Since he took over the family estate in 1996 he’s installed other modern winemaking equipment, such as temperature-controlled stainless-steel fermentation tanks, launched mono-varietal wines (Malbec and Cabernet Franc), planted the estate’s first Sauvignon Blanc, and abandoned the region’s tradition-bound packaging in favor of labels that are “chic and trendy.”

He has become an advocate of the densimetric sorting table because he is convinced it provides “the nearly perfect sorting of the grapes…It enables us to work at the heart of the berry.”

Use of the machine also helps address the matter of finding and paying workers qualified to sort grapes visually. “Before the densimetric sorting table we had good results with four people sorting the harvest by hand, but we always want to improve. We cannot remain comfortable, so we challenge our work every year. With the machine we are focusing on details in order to evolve our quality and our modernism,” Lhuillier said.

Just nine other estates in Bordeaux use the table, he added.

Adoption Slow in the United States

In California, vintners have been slow to adapt the Delta Densilys, perhaps because it is so new or perhaps because vintners here generally are able to get their grapes ideally ripe, speculated Mea Leeman, sales and marketing director for Bucher Vaslin North America in Santa Rosa. Winemakers who have experimented with the machine have used it more to wash grapes than to determine ripeness, she added. She said the company will be more assertively marketing the machine this year, following refinements introduced based on experience with the units during last year’s harvest in South America.

A Napa Valley winemaker who used the densimetric sorting table for the first time this past harvest to sort Cabernet Sauvignon saw mixed results. He said the system was cumbersome to set up and learn, demanded a large amount of sugar to get the solution he wanted, required that the bath be changed more often than anticipated, and diluted the wine, lowering its expected alcohol. “Just a touch, not dramatically,” he said. 

“If I found others were having success with it I would try it again. We have to be open minded in this world today. We are always looking at opportunity,” said the winemaker.

Some other members of the California wine trade expressed concern about the potential impact of the technique on the nature of the resulting wine.

Alison Crowe, winemaker for Garnet Vineyards of Napa, and author of “The WineMaker’s Answer Book,” mused whether dunking grapes in a bath might scrub the fruit of microbes, yeast and the like, all which contribute to the character of the ultimate wine.

“If you rinse off grapes, even if they are drained (as they are with the Delta Densilys), you’ve fundamentally altered the native flora. What are you rinsing off those grapes? If a producer is relying on a special mojo of microbes, you might be losing something. That’s a big concern for me,” said Crowe, who hasn’t worked with a densimetric sorting table. “Sorting mechanisms may get grapes too clean. We want complexity, layers. You may be sorting out too much.”

Andrew Waterhouse, director of the Robert Mondavi Institute of Wine and Food Science at the University of California, Davis, expressed a similar concern, noting that the goal of getting more uniformly ripe grapes also means the fruit will be more homogenous. “Compared to traditional winemaking, this would eliminate flavors that have traditionally been present. This usually means eliminating vegetal/green flavors. While this is usually considered favorable, it does remove flavors that have traditionally been associated with Cabernet Sauvignon. This will have a related impact,” Waterhouse said.

Anita Oberholster, also with UC Davis as associate specialist in cooperative extension in enology, concured. “Sometimes having more heterogeneity is good as it allows for a more complex flavor profile,” Oberholster said.

She has conducted tests with three types of optical sorting, finding that Cabernet Sauvignon from unsorted grapes is equal to or even better in flavor complexity and body than wines from grapes sorted by various methods. “A lot depends on the stylistic focus of the winemaker.”

She said the densimetric sorting table is the latest chapter in the ever-evolving playbook of decisions winemakers face as they bring grapes from vineyard to cellar. Other chapters include the time of day to harvest, the kind of weather at harvest, the kind of transportation used for the fruit and so forth. “Everything that is done upstream of the fermentation is impacting the grape-associated microbes and selecting for certain microbes over others,” Oberholster said.

Meanwhile, back in Bordeaux, Lhuillier said he hasn’t seen any material impact on the character of wines he has been making with grapes that have gone through the Delta Densilys densimetric sorting table. Alcohols have been unaffected, and he is confident his wines continue to reflect his stylistic goals and the terroir of his vineyards. “According to my observation, the machine cleans the berries but does not attack the skin of the bunch and does not attack the indigenous flora,” Lhuillier said.

Whether such sorting machines become a staple of tomorrow’s winery is up in the air. They could face stiff competition in infrared-spectroscopy and hyperspectral-imaging technologies that are being tested on various fruits, including wine grapes, to determine their ripeness, notes Waterhouse.

“I expect this (newer) technology will eventually displace something like this (densimetric sorting tables),” Waterhouse said. With such imaging, a vineyard worker or a drone theoretically will be able to pass through a vineyard while pointing a gun-like device at clusters of grapes to gather data on total soluble solids, including sugar and acidity. Such a tool would have a twofold advantage over densimetric sorting tables – the data gathered would be more comprehensive and the grapes wouldn’t need to be harvested beforehand.

“I’m not sure how close we are to this,” said Waterhouse. “It may be five years away if everything falls into place. People definitely are scrambling to do this.”

 

 


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