How Are Raisins Made?
Raisins are made from grapes that have been dried in the sun or by artificial heat. To make sun-dried raisins, sweet, seedless grapes are cut from the vines and spread out to dry on large sheets of brown paper. Sunshine turns the grapes into raisins in about three weeks.
The raisins are then taken to the packing plant where special machinery removes the dirt and stems. They are poured into a hopper which feeds onto a series of conveyor belts and drums that remove any remaining stems, chaff or light weight fruit.
Then, the raisins are sent through a brisk vacuum air stream to catch any undesirable material that may have been missed.
Then they are size-graded and thoroughly washed. The raisins then move past a sophisticated laser sorter that uses light beams and a computer to determine if anything other than raisins is passing through the stream.
If the computer determines something is not a raisin, it instantly sends a small burst of air to knock the material out of the stream into a trough below, all at incredibly high speeds!
Hand inspections are done throughout the packaging process by quality control technicians. Next, the cleaned raisins are put into large wooden bins, called sweat boxes, to equalize their moisture content. Finally, the raisins are washed, inspected, and packaged.