Renfu Lu heads the team that developed the apple harvester/sorter. The demonstration started sorting apples from crates and then moved into the orchard. Photo by Richard Lehnert

Renfu Lu heads the team that developed the apple harvester/sorter. The demonstration started sorting apples from crates and then moved into the orchard. Photo by Richard Lehnert

Storing apples is expensive, and storing bad apples is even more so. If you’re going to toss out a cull apple, the best time to do it is immediately.

Some packers have gone to prestorage sorting in the packing house. But for growers without packing lines who rent or use their own storage for sales later in the season, a different solution would be helpful.

Dr. Renfu Lu is working on that solution.

In September, Lu and his team of USDA Agricultural Research Service agricultural engineers working at Michigan State University demonstrated their prototype mobile in-orchard harvesting and sorting machine in a block of Gala apples in Brett Anderson’s orchard near Sparta, Michigan.

The machine looks very much like the Munckhof Pluk-O-Trak, with its flexing conveyor arms taking in apples as pickers deposit them. Two workers riding on platforms pick high apples and two walking on the ground pick low apples. That’s how the apples get to the sorting device.

The sorting module looking like those “magic boxes” on packing house lines where apples are photographed multiple times from many angles and their color, size, and external defects identified. And it is. A computer keeps track of each singulated apple as it continues its path toward a bin reserved for others like itself—in this case, fresh market quality apples, processing apples, or juice apples.

This machine also has a novel bin-filling device Lu said was designed in-house by his team of engineers.

The key, however, is price. Lu thinks the machine can be manufactured from off-the-shelf parts for less than $30,000, making it practical for smaller growers. The camera itself is cheap, he said, selling for about $150. A laptop-like computer equipped with a microchip and a program dictates the apple parameters—size, color, weight, shape, etc.

The computer can be trained. The person running the machine can pick an apple, place it before the camera, and show the computer, “these are the kind of apples I want in the fresh-market bin.”

More culls, more benefit

“The higher the percentage of culls, the more the economics favor the machine,” Lu said. Growers in the Midwest and Northeast have not achieved the high level of fresh market quality apples that growers in the Pacific Northwest have, he said, so the machine may be better suited for them. The machine would be quite useful in orchards where a lot of fruit was damaged by hail, for example, or where color was a problem, and the job was to salvage the good apples for the higher-price market or to eliminate apples that might rot in storage.

Development of the sorter has been under way for about three years, Lu said, with some funding from the Michigan Apple Committee. Lu’s team includes fellow engineers Drs. Akira Mizushima, Haiyan Cen, and Fernando Mendoza.

“In general, processing apple growers do not expect to sell apples in the fresh market,” Lu and Mizushima wrote in a paper assessing the costs and benefits of in-field sorting. “With adoption of an in-field presorting system, processing apple growers can sell some fresh apples from the apples that are originally destined for processing,”

That would be most useful to growers in Pennsylvania, where 70 percent of the apples go for processing, and least useful in Washington, where only 16 percent go to processing. In Michigan, 65 percent go to processing, 55 percent in California, and 47 percent in New York.

“Reducing the cost, that was the big concern,” Lu said about designing the harvester/sorter. “We have a simple design using generic components. The sorter can handle six to eight apples per second, which is fast enough for a crew.”

One idea for cost saving was to build the machine to fit existing machines. It is mounted on a Phil Brown Welding Co. trailer designed to haul five bulk bins. On the day of the demonstration, three bins were used. The machine is not self–propelled; it is pulled by a tractor.

Bin filling and handling

The design of the bin filler seems quite simple. Once an apple reaches its assigned bin, it drops two to three feet, guided by “curtains” that keep it on track until it reaches foam rollers that break the fall and pull the apple down into a revolving elephant-ear fan that distributes it gently in the bin.

“Bin changing was a big challenge,” Lu said. The four bins on the trailer move easily in and out on the chain bed, but in sorting the bins don’t all fill at the same rate. So the grower will handle some full bins and some only partially filled.

The computer can be directed to change the location where it drops an apple, so some adjustment is possible by switching the drop from one bin to another. It’s possible to fill two boxes of one grade and partially fill one each of two other grades. “It is much easier to work with two grades and four boxes than it is with three grades,” Lu said.

Pickers on his machine worked on fixed platforms, which worked well in the Michigan orchards’ closely spaced rows and ten-foot-tall trees. Making the platform so it would move up and down, in and out, would add to the cost, Lu said, but could be done.

“It did what you wanted it to do,” said Phil Schwallier, Michigan State University Extension fruit educator, looking at the bins after the demonstration. “It sorted the apples into three grades.”

Schwallier has been involved in monitoring quality of apples harvested by machines like the DBR Conveyor Concepts machine that moves apples by vacuum tube as they are picked. The DBR is being built at Phil Brown Welding, located close to the demonstration orchard.

The demonstration drew several growers interested in the machine, and Phil Brown, co-developer of the DBR machine, was there as well.

The economics

Lu and Mizushima published an economic analysis. They figure their machine could, in 45 days of harvest, handle 1,768 bins of apples. “A $30,000 machine will be beneficial for growers of more than 1,400 bins if the cullage rate is 20 percent,” they wrote. “If the cullage rate is more than 40 percent, even a $40,000 in-field presorting machine can be beneficial for small-size fresh apple growers.”

The numbers were based only on the packing house cost for culls and did not include labor savings with the harvest-aid machine.

If processing apple growers could skim off the cream of their crop, just 10 percent going into the fresh market, a $30,000 machine could benefit a grower having only 1,200 bins of apples, they say.

Packing houses could also benefit from having its growers use the orchard presorting machine. “Presorted apples are more consistent in quality, thus enabling packing houses to better manage postharvest storage and packing operations,” they stated in their paper.  •