Raisins are dried grapes/currants. However, unlike fresh grapes, they indeed are rich and concentrated sources of energy, vitamins, electrolytes, and minerals. On a weight per weight comparison basis, 100 g of dried grapes hold 249 calories, several times more fiber, vitamins, minerals and polyphenol antioxidants than the fresh grapes. Raisins, however, contain fewer amounts of vitamin-C, folic acid, carotenes, lutein and xanthins than fresh grapes.
In general, fresh grapes, either seedless or seed types of the Vinifera species such as Thompson seedless (Sultana), Sugarone, Calmeria, Corinth, etc., are subjected to dry under sunlight or mechanical drying techniques. In some cases, the whole bunch of grapes may be allowed to dry on the plant itself (vine-dried). Ordinarily, their moisture content should not exceed 16% of dry weight. Thoroughly dried raisins are then further stemmed, cap-stemmed, sorted and cleaned in order to obtain high quality, dried berries. At the wholesale level, raisins are processed and graded further before sent to the markets.