A raisin is a dried grape. Raisins are produced in many regions of the world and may be eaten raw or used in cooking, baking, and brewing. In the United Kingdom, Ireland, New Zealand, and Australia, the word “raisin” is reserved for the dark-colored dried large grape, with “sultana” being a golden-colored dried grape, and “currant” being a dried small Black Corinth seedless grape.
The word “raisin” dates back to Middle English and is a loanword from Old French; in modern French, raisin means “grape”, while a dried grape is a raisin sec, or “dry grape”. The Old French word, in turn, developed from the Latin word racemus, “a bunch of grapes”.
Raisin varieties depend on the type of grape used and are made in a variety of sizes and colors including green, black, brown, blue, purple, and yellow. Seedless varieties include the sultana (the common American type is known as Thompson Seedless in the United States), the Greek currants (black corinthian raisins, Vitis vinifera L. var. Apyrena) and Flame grapes. Raisins are traditionally sun-dried, but may also be water-dipped and artificially dehydrated.
“Golden raisins” are generally dried in dehydrators with controlled temperature and humidity, which allows them to retain a lighter color and more moisture. They are often treated with sulfur dioxide after drying.
Black Corinth or Zante currant are miniature, sometimes seedless raisins that are much darker and have a tart, tangy flavor. They are often called currants. Muscat raisins are large compared to other varieties, and also sweeter.
Several varieties of raisins produced in Asia are available in the West only at ethnic grocers. Monukka grapes are used for some of these.
Global production in 2016 was 1.2 million metric tons, with the US as the top producer contributing 24% of the global harvest.
Raisins are produced commercially by drying harvested grape berries. For a grape berry to dry, water inside the grape must be removed completely from the interior of the cells onto the surface of the grape where the water droplets can evaporate. However, this diffusion process is very difficult because the grape skin contains wax in its cuticle, which prevents the water from passing through.In addition to this, the physical and chemical mechanisms located on the outer layers of the grape are adapted to prevent water loss.