The Scoop on Machine Harvesting Wine Grapes
For this newsletter, we decided to interview Airfield Estates owner and wine grape grower, Mike Miller, about harvesting wine grapes with a machine. We know this is a mysterious part of the wine process for a lot of wine drinkers out there and knew that Mike would be able to shed some light on the topic.
How does mechanical grape harvesting work?
In short… A grape harvester is a tall machine that straddles the trellis and uses special fingers (or rods) to shake the grapes off the vine.
For our technical readers….On our farm, we use Korvan Grape Harvesters. Our machines use a set of bow rods placed in close proximity to each other on each side of the fruiting zone. These rods freely float through the canopy as the harvester rolls through the field. The rods oscillate at a fairly high number of beats per minute. Meanwhile, the vines move back and forth in time to the picking rods, and the grape clusters (whose stems have become mature & somewhat brittle) drop toward the vineyard floor.
After the grapes have been shaken off the vine, the fruit lands on a catching tray, is collected by conveyor cups, and then transported to a cross conveyor that sits high at the rear of the machine. As the grapes drop onto the cross conveyor, two large fans pull out all of the light debris (such as leaves).
Then the grapes are transported to the discharge conveyor where they are screened by a third fan and by an inspector, who pulls out any foreign material (such as grape wood).
The fruit continues to move along the conveyor toward a trailer (catch bin) that travels in the row next to the harvester. Before the grapes enter the catch bin, the final screening is performed by a high power magnet, which removes any metal (wire or clips) that may have been caught by the picking rods.
Does it save on labor in the vineyard?
Our machine harvest crew is able to harvest as much as 200 tons in a shift. That crew is composed of 8 people. On the contrary, it typically takes 30 hand pickers to harvest 20 tons in a 10 hour shift. Machine harvesting not only allows us to save on labor costs, but also gives us the opportunity to harvest our fruit in a more timely fashion.
Does machine harvesting damage wine quality?
If grapes are not pressed in a timely manner after mechanical harvest, wine quality may be compromised. We insure that grapes are delivered within an hour of harvest. This is possible because of the close proximity of our vineyard to the winery. Furthermore, in order to mitigate the effects of the harvester, we harvest all of our fruit early in the morning. This means that the fruit is delivered in a chilled state, which helps insure that early fermentation will not be initiated.
What grapes are suitable for machine harvesting?
In general, mechanical harvesting works well for the thicker-skinned grapes (such as Merlot and Cabernet Sauvignon). Thin-skinned grapes (such as Pinot Noir) are more delicate, and the berries pose a greater risk of rupturing and being susceptible to oxidation.
The physical characteristics of the vineyard (such as the type of trellis, space between rows, & the slope) also play a role in determining whether mechanical harvesting is feasible.
Weather is another factor. A formidable weather forecast might encourage mechanical harvesting to get the fruit off the vine in a more timely fashion. On the contrary, the early killing frost of the 2009 season caused us to hand-pick nearly every red varietal. We were concerned that machine harvesting would cause the dry, brittle leaves to become pulverized, be too difficult to remove from the grapes, and cause the wine to take on an undesirable vegetal character.
On our farm, we are fortunate that we have the ability to both machine harvest and hand-pick. This allows us to be more strategic about how we can process grapes in the most efficient and effective manner without compromising quality.
Do grape harvesters miss a lot of the fruit?
I truly believe that a hand crew leaves more fruit in the vineyard then the machine. This has not always been the case. The early harvesters were not as efficient at grape removal. We find that many home winemakers are extremely disappointed when given the opportunity to glean fruit because very little is left behind after the harvesters roll through the vineyard.
How do I get hired as a grape harvester driver? It sounds like fun.
Our entire machine harvest crew is comprised of full-time employees. When we get into the harvest season, everyone has his or her particular expertise. The main job requirements are: (1.) Be dependably early. We traditionally start at midnight. (2.) Good night vision. At least 60% of our grapes are picked before the sun rises. Trying to determine picked from unpicked rows can be difficult, & once the machine enters a row, it can not back up. Some of the rows can be up to ½ mile long. Pulling into the wrong row will result in a few expletives. (3.) Be able to deal w/ sleep deprivation. Universally, no one ever gets enough sleep during harvest. (4.) It is important that each member of our crew have a healthy appetite. Midnight snacks, donuts at break, big country breakfast mid-morning, & lunch breaks after the pick are a rule of order. I’ve always found that harvest can be good for at least 10 pounds.