Growing & Winemaking


Getting the MOG Out

December 2010
by Peter Mitham
wild goose
Roland Kruger watches whole clusters fall into the destemmer at Wild Goose Vineyards. Photo by Peter Mitham
One of the best ways to keep juice and must clean is to make sure nothing else gets into the bins when the grapes are harvested; but invariably, something will always tag along. If you’re using manual harvesting, there are always parts of the stem and leaves that somehow reach the bin. Soil, rocks and sometimes even small animals hitch along for the ride to the crush pad. And critters definitely don’t belong in your wine—even if it’s a critter wine.


  • Avoiding material other than grapes (MOG) begins in the vineyard with careful harvesting.
  • At the crush pad, new equipment enables cluster sorting and berry sorting options that eliminate many vegetal flavors and coax the best elements out of difficult harvests.
  • Some wineries use the equipment to over-deliver at various price points, seeing increased demand and the potential to raise prices.
That’s why Roland Kruger, co-owner of Wild Goose Vineyards in Okanagan Falls in British Columbia’s Okanagan Valley, keeps a close eye on grapes even before they’re poured into the winery’s destemmer, an eight-year-old Enoveneta system supplied by Criveller.

“We grow a lot of our own fruit, so we’re very cognizant of what’s happening out in the vineyards when we’re picking,” he says as a bin of Pinot Gris falls into the destemmer. “And because we process the grapes so quickly, we know if anything’s ending up in the bin, so we can talk to our workers right away.”

The approach has virtually eliminated the MOG (material other than grapes) in the fruit he receives, with just the odd leaf showing up. A small operation, Wild Goose also ensures vines are trimmed to limit the canopy’s interference with harvest. Plastic bin liners and careful handling of the bins themselves to prevent soil or sod from clinging also help prevent foreign objects from mixing with the grapes.

“MOG, it’s not part of our equation; we make sure there’s nothing in the fruit,” Kruger said. “No stems make it through the process. The leaves also have a tough time making it through here as well....It’s just berries and the seeds of the berries.”

Paddles in the cylinder of the destemmer gently knock fruit off their stems. The berries drop through rollers that gently split them enough to get the juice flowing, and they’re driven to a peristaltic pump that pushes grapes, juice—and little else—along to the press.

While the hands-on approach suits Wild Goose, whose wines have a potential to age gracefully, a more sophisticated sorting line was needed at nearby Blasted Church Vineyards. Blasted Church has grown its production to approximately 20,000 cases per year from less than 1,000 cases when owners Chris and Evelyn Campbell acquired it in 2002. At twice the size of Wild Goose, it has doubled its production since winemaker Richard Kanazawa arrived in 2007.

“They were still doing 10,000 cases, and they wanted to increase production,” he said of the plan when he joined. “But if you’re going to increase production, you have to maintain quality as well.…And not just maintain quality, but up it.”

To ensure quality kept pace as production increased, Blasted Church acquired an inclined sorting table from P&L Specialties. It allowed whole-cluster sorting to remove rotten clusters, leaves and other MOG prior to the fruit entering a Zickler destemmer. An elevator ensured clusters flowed evenly, at a rate of one ton every 10 minutes.

“You’re seeing a lot more of these in the valley, and it makes sense to have one, because you can sort whole cluster, and that to most people is the most important thing.…To sort whole berry, it’s got to be pretty ugly stuff,” Kanazawa said.

The berries drop from the destemmer onto a short sorting table where two to four workers pluck jacks and remaining debris from the grapes as they move towards a hopper en route to the tank.

Kanazawa says the system isn’t ideal for tight-clustered or sensitive varieties such as Pinot Blanc, Pinot Gris and Pinot Noir, as the grapes can be damaged and too much juice lost, but it does eliminate most of the garbage that can affect the sensory attributes of Blasted Church’s wines, which tend to be fresh with appealing aromatics fostered in the cool-climate Okanagan.

Gentle handling is important to Kanazawa because it means berries remain whole, limiting exposure of seeds in the must and the release of compounds into the wine that may be worse for the wines than those in the vegetative matter to which the grapes are attached. Moreover, he says some wines can be too clean, which he feels detracts from the character. He would rather receive clean grapes, get rid of as much MOG as possible and let the rest express itself.

 “There’s a lot of wines that I don’t sort (the grapes) because they come in from the vineyard clean,” he said. “For instance, if I’m going to put a white wine into a press, maybe there are some stems in there, but it’s not going to spend very much time. The wine’s not going to be stemmy. Do you want to use all this equipment to remove some stems that don’t really matter anyway? For me it’s a lot of time and money to do that when it’s not going to affect quality in any significant manner.”

Sensory benefits

An effective sort can deliver noticeable sensory improvements to wine. Speaking to the British Columbia Wine Grape Council conference in Penticton, B.C., earlier this year, Dr. Kevin Usher of the Pacific Agri-Food Research Centre told growers the pyrazines from a single grape would impart a distinct flavor to 500,000 tons of fruit.

Pyrazines are the compounds responsible for the bell pepper character apparent in Sauvignon Blanc from New Zealand, for instance, as well as green pea and occasionally beetroot. They’re found in all green tissues of the grape, and levels may reflect ripeness, although levels vary by variety and even clone. Cabernet Sauvignon, for instance, harbors the largest concentrations in the stem and skin, with seeds harboring the least.

White wines are particularly sensitive, with pyrazine levels of 1 to 2 nanograms per liter becoming apparent while red wines with their richer mix of sensory characters can accommodate 10 to 15 nanograms per liter.

While some manifestations are pleasant and even desirable, pyrazine levels can be a challenge in cool-climate regions such as the Okanagan.

“The berries might be ripe, but the stems and the stalks may not always be ripe,” said John Simes, winemaker at Mission Hill Family Estate near Kelowna. “That’s just the reality of the Okanagan Valley.”

But if too many stalks and stems make it through to fermentation, the wine may require greater attention to eliminate the green and leafy characters than a wine made from clean fruit.

“The more that you can get out—the more you get whole, sound berries—the riper your tannins are going to be,” Simes said. “You’ve dumped off a lot of that extra green phenolic stuff.”

Sorting the grapes using efficient sorters makes the task of removing the green elements easier from the start. While green and unripe bunches can be steadily weeded out through the season, the stalks and stems will follow the grapes into the winery, where most estimates peg them at about 2% of a given bin.

“Most of it’s in the stem in the whole cluster, so it’s really important to remove any green material before it goes into making wine. So this includes destemming,” Usher told growers in Penticton. “This has been reported to reduce these pyrazine levels.”
Black Hills Estate Winery on the Black Sage Road opposite Oliver also refrains from heavy sorting or destemming for some of its white winegrapes, such as Sauvignon Blanc, which is whole-cluster fermented.

But that didn’t stop Black Hills from spending approximately $50,000 on an Armbruster RotoVib destemmer and two-foot vibrating Mistral sorting table from Vauchet Beguet. The two paid for themselves during the 2009 harvest, when an early October frost cut short the season, and the incoming grapes required greater attention on the crush pad to weed out dry leaves and damaged fruit.

“It was fairly inexpensive in the big picture,” winemaker Graham Pierce said. “With the frost last year, it paid for itself.”

Sorted berries, once destemmed, fall on a vibrating grate where shot berries and other debris fall through. A sorting table allows workers to remove any outstanding pieces, but Pierce says the genius of the system is an air knife at the end of the sorting table that blows away any remaining debris as berries fall towards the pump. It’s an elegant solution that reduces the manual sorting required while significantly boosting the quality of grapes that make its premium wines.

Indeed, the whole system was so gentle on the grapes that Black Hills bought a pair of rollers to crush some of its white fruit that wasn’t adequately broken during sorting and pumping.

A similar but larger system at Mission Hill Family Estate near Kelowna provides similar quality, so much so that winemaker John Simes has expanded the system’s use during the past six years from grapes destined for its top-tier wines to some of its reserve-tier labels.

An elevator feeds grapes to a Bucher E2 destemmer whose chamber and paddles both turn to evenly move grapes to the 140cm Mistral sorting table. Simes shares Pierce’s passion for the system’s air knife and notes that it significantly reduces the sorting that attendants have to do. “It’s doing quite a lot of presorting already,” he said.

The end result is top-quality fruit moving to fermentation and better quality wines. “We’re just liking the quality better that we’re getting out of it,” Simes said. “So we’re using it as much as we can.”

The price of the finished wines reflect the greater care being taken. Grapes for Mission Hill’s top-tier items such as Oculus and Legacy-series wines, as well as its Select Lot Collection, are harvested by pickers receiving an hourly rate to ensure greater care. The grapes move across the sorting table into wines retailing for CAD$22-$80 per bottle.

But the system’s efficiency has allowed Mission Hill to improve the quality of even its reserve tier wines, which retail at the winery for approximately CAD$19-$22 per bottle.

“The quality’s going up and up and up, and that’s translating into more volume of sales or maybe even a higher price, or both,” Simes said, making the economic argument for mechanized sorting.

While some wineries have shifted upper-tier fruit into value-priced blends as consumers retrenched, Mission Hill has leveraged its equipment to ensure the best fruit makes it into designated blends, over-delivering on quality.

“We have to have a very good idea of what block is going to end up in the bottle,” he said. This equipment has “allowed us to go into the vineyard and pick very small pieces of the vineyard—like down to two and three acres—and keep them as separate batches.”

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