Dry Grapes are dried in the sun in their natural condition; they are grayish-black or grayish brown, with the natural bloom intact and rather tough skin. Golden-bleached raisins are produced from Thompson Seedless grapes dipped in 0.5 percent lye and exposed to sulfur dioxide after drying. What is dry grape? Raisins are a type of grape that has been dried for around three weeks. Grapes darken as they dry, which gives raisins their dark brown color. A range of grape varieties is used to make raisins. Dried grapes are rich in iron, copper, and Vitamin B complex. Eating some raisins every day would ensure that there is no iron deficiency and prevents anemia. Raisins have a high level of the polyphenolic antioxidants catechins, which neutralize free radicals.