Most raisins now, however, are produced from “seedless” grapes, usually Thompson Seedless grapes. This both helps ensure that the consumer doesn’t get any raisins with seeds in them that might have been missed during a de-seeding process, and eliminates the producer’s cost of having to seed them in the first place.
Most seedless grape varieties in the United States derive from crosses between Thomson Seedless and Black Monukka.
Many seedless raisins aren’t in fact seedless: the seeds are there, but are so undeveloped that they are undetectable.