Yesterday we went over to Dallas, Oregon, where friends of friends were conducting their annual prune harvest. It was quite fascinating. A pair of machines with interlocking tarp-like structures comes up to each prune tree and then one of them gently grabs the tree trunk and shakes the tree. All the ripe prunes fall onto the tarps where they roll to the center and then to a field crate measuring maybe 4 x 4 x 2.5 feet. Then they are taken to the processing building where they are poured into a vat of water for basic cleaning. They then go over a grill-like rack where sticks and leaves are removed and undersized prunes fall into a trash box. Then the prunes go to a sorting table where a couple of people go over them and cull out any bad ones and any remaining leaves and twigs. At this point they are in single layers on racks measuring about 3 x 3 feet. A stack of racks about 6 or 7 feet high is then loaded into a drying oven. These are rooms maybe 8 feet high and ten feet wide and 20 feet deep. When the room is full they close the door and leave the prunes in there for about 24 hours. The rooms are heated to 160 degrees with massive gas jets and hurricane force winds. I went in one and can tell you it's damn hot and windy in there! When the prunes come out they are the dried prunes you are familiar with. Actually you're NOT familiar with these particular prunes because the entire crop, which has golden meat rather than the black we usually see, is sold to retailers in Japan.
We went out into the orchard a couple of rows ahead of the harvesting machines and picked our own fresh prunes. We came home with two big bags of them, and will slice and pit them this afternoon and store them in the freezer.
If you think prunes are just dried plums, you're partly right. Fresh prunes are a variety of plums, but much meatier than most plums. If you dried a normal plum the way the prune makers do, you'd end up with a pit inside a wrinkled bag of skin. No meat to speak of. They are mostly water.
The amount of waste is amazing. The prunes are harvested from each tree three times, about a week apart. By the time the harvest starts many ripe prunes have already dropped to the ground, and between shakings many more join them. After the final run-through there still are many prunes on the trees, but not enough o be harvested economically. So while each tree produces many, many prunes (hundreds per tree) hundreds, maybe a third to a half, never leave the orchard and rot on the ground. Fertilizer, I guess.