Sorting the MOG from the must

Key Technology has conducted several full-season trials with wineries in North America, Europe and Australia to verify the effectiveness of its VitiSort sorter for red wine grapes.

Suitable for wineries producing 5000 to 50,000 cases per year, VitiSort sorts up to five tons of red grapes per hour, removing MOG (material other than grape) such as insects, skins, raisins, shot berries, petioles and leaves from the product flow. This enables the winery to better control the quality of must going to the fermentation tanks.

Both Pepper Bridge Winery near the Washington-Oregon border and Chateau Ste Michelle in Woodville, Washington, have used VitiSort for more than one vintage.

“With its MOG shaker and optical sorter combined, VitiSort is very effective at improving the quality of our must. If it’s not removed, MOG will release a bitterness - a harsh tannin - to the wine. Removing the non-grape attributes like this will improve the quality of our wine,” said Jean-François Pellet, Winemaker at Pepper Bridge Winery.

“Thanks to this system, we’re able to receive, sort and crush 3.5 tons of grapes per hour with only four workers. One is overseeing the operation, one is feeding product to the system, and two are sorting out leaves before the destemmer. It’s hard to say how many people we would need without VitiSort - maybe 15 or 20, I’m not sure - but it’s virtually impossible to achieve this high level of MOG removal at the volume we’re doing with manual labour.”

“With Key’s VitiSort, we’re removing 99.9% of the MOG while sorting 4 to 5 tons of grapes per hour with two and a half workers,” said Ray McKee, Red Winemaker for Chateau Ste Michelle.

“The effectiveness of the technology allows us to use machine-picked grapes and put only berries and pure juice into fermentation. It gives us exceptional quality control to end up with a very rich and dense wine that doesn’t have the tannin from green stems and leaves.”

The stainless steel VitiSort is compact and mobile, designed to easily roll into position under the destemmer so fruit automatically flows from one machine to the other. The two-stage VitiSort features a mechanical MOG removal system followed by an optical sorter.

First, a vibratory conveyor gently shakes the grapes to separate MOG, which falls through uniquely designed slots in the shaker’s screen, along with juices. MOG is accumulated on a sloped surface for easy disposal, while the juices are recovered for reintroduction to the must. Singulated grapes freefall from the end of the vibratory conveyor into the sorter, presenting a ‘sheet’ of product that allows a camera to inspect each grape. A specially designed drip tray keeps juice out of the camera line of sight. The sorter quickly analyses the images, comparing each object to previously defined accept/reject standards. When unwanted objects are identified, the sorter activates the ejector system, which is made up of a series of air jets that span the width of the system. While still air-borne, the air jets pinpoint MOG to reject and remove it from the product stream. Grapes are discharged from the sorter into a trough or screw conveyor for delivery to the fermentation tank.

Compared to sorters that feature horizontal belts to inspect product on a horizontal plane, Key’s VitiSort inspects product on a vertical plane to simplify the operation while achieving the same results. VitiSort offers a smaller footprint, improved sanitation with the elimination of belts and gentle handling with fewer transitions.

Key says the VitiSort can do the work of 8 to 12 people, and yield loss associated with the sorter is 2 to 4%, depending on the grape variety and the effectiveness of the destemmer. A colour touch-screen panel features a graphical user interface where the winemaker can adjust the sort parameters to remove more or less MOG to meet requirements. Product settings can be stored and retrieved.

VitiSort can function along with the destemmer or combined with Key’s Grape Receiving and Inspection Platform (GRIP) upstream of the destemmer.

“The MOG shaker is very effective at removing insects and shot berries, which reduces the load on the optical sorter and improves its performance. The optical sorter takes out stem jacks and other MOG,” said Pellet. “It’s a very simple, gravity-fed system. Since it has no belts, it’s easy to use, easy to clean and easy to maintain.”