Prune
Aiton's Encyclopedia (1910)
in horticulture, a plum suitable for drying; in commerce, a dried plum. Ordinary plums cannot be dried whole. They will ferment or sour before they dry out sufficiently to keep. Prune plums are not thin fleshed, quite the contrary; but they contain a large amount of sugar and can undergo the same treatment as raisin grapes. France, with an annual output of 70,000,000 pounds, has been the leading country in prune production, but of late California has taken the lead. Oregon, Washington, and Idaho very nearly equal the output of California. Spain, Mediterranean France, and the eastern shore of the Adriatic export prunes in large quantities. The drying of prunes is an interesting operation. The fruit is allowed to ripen until it falls from the tree. It is then passed over grates or large sieves which sift out rubbish and land the fruit in several piles according to size. The prunes are then pricked to allow the escape of moisture; or else they are run on endless aprons through lye to weaken the skins. After that they are placed in wire-bottomed trays and are either evaporated in a drying house by exposure, for from twelve to forty-eight hours according to size, to heat increasing from 120 deg. at the start to 180 deg. at the finish, or they are dried by exposure to the sun for five to twelve days. If drying be over hasty, the fruit will be hard and lacking in flavor. Unless the drying be thorough, the fruit will not keep. Prunes are graded as 30's, 40's, and so on, to 120's and 130's, according to the number in a pound. See Plums
What Has Changed in the Last Century
Aiton's 1910 note that "of late California has taken the lead" over France proved permanent: the Sacramento Valley, planted almost entirely to the Improved French d'Agen variety, has supplied most of the world's crop for decades, while the Oregon, Washington and Idaho industries that Aiton said "very nearly equal" California's have all but disappeared. The word itself has changed too. Around 2000 the California Prune Board renamed itself the California Dried Plum Board and won permission to label the fruit "dried plums," hoping to shed the laxative associations that had made "prune" a joke word. The drying itself still follows Aiton's recipe closely, though fruit is now shaken from the trees by machine rather than left to fall, and tunnel dehydrators have replaced sun-drying almost entirely; the old count-per-pound grading (30's to 130's) survives in the trade.
Written for this edition, 2026.