- 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.[6] However, this diffusion process is very difficult because the grape skin contains wax in its cuticle, which prevents the water from passing through.[6] In addition to this, the physical and chemical mechanisms located on the outer layers of the grape are adapted to prevent water loss.[7] The three steps to commercial raisin production include pre-treatment, drying, and post-drying processes.[6]
- The three types of drying methods are: sun drying, shade drying, and mechanical drying. Sun drying is an inexpensive process; however, environmental contamination, insect infections, and microbial deterioration can occur and the resulting raisins are often of low quality. Additionally, sun drying is a very slow process and may not produce the most desirable raisins.[6]
- Mechanical drying can be done in a safer and more controlled environment where rapid drying is guaranteed. One type of mechanical drying is to use microwave heating. Water molecules in the grapes absorb microwave energy resulting in rapid evaporation. Microwave heating often produces puffy raisins.[6]
 Raisins  Golden Raisin  Dried Raisin  Black Raisins |  Green Raisin  Yellow Raisins  Munakka  Brown Raisins |  Malayar Raisins  Seedless Raisins  Red Raisin  Paan Raisins |
