Piña Napa Valley: Optical Grape Sorter to the Rescue

So what do you think this mechanical monster is and does?

2010 was a difficult year for most grape growers in the Napa Valley. It was unseasonably cool through most of the growing season and the grapes were maturing later than usual. Notice that I didn’t say it was an abnormal year. That would imply that some years are normal and it doesn’t seem that we’ve had anything I could refer to as “normal year” in a long time. Tedious leafing had exposed the grapes to direct sunlight, just as planned. Just when we were beginning to think that we might make it to harvest without any major concerns, we got hit with a heat wave. It was an intense heat wave. It was as if Mother Nature woke up and decided to make amends for the cool summer.

Things looked bad. We had grapes turning to raisins, especially on the sunny side of the clusters. I have read, and believe, that the single most important factor for quality wines is a uniform crop. But with the raisins, our crop was less than uniform.

Anna, our winemaker, suggested a fairly expensive solution to this dilemma. She suggested we use an optical sorter. We had to decide between spending lots of money for top quality grapes or producing something less than top quality wines. When we looked at it that way, we had no choice.

So our good friends at Walsh Vineyard Management had an optical sorter that we could rent.

So what exactly does an optical sorter do? This is the amazing part.

An optical sorter looks at each berry and decides if it is worthy of being made into quality wine.

Did you catch that … “each berry”? So how does it do that?

Thomas Ulrich, in an article for Wines & Vines, described the process like this:

“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.”

In this YouTube video, you can see the optical sorter in operation. Unfortunately, you can’t see the air jets actually blasting away at the substandard berries, but you can see the speed at which the berries travel down the conveyor. As you watch the video, keep in mind that each of those speeding berries is closely evaluated before they can make it past the air jets and into the “keep” bin.