A raisin is a dried grape. Raisins are produced in many regions of the world and may be eaten raw or used in cooking, raisin bread, and brewing. French, raisin means “grape”, while a dried grape is a raisin sec, or “dry grape”.

California seedless grape raisins on the left and California Zante currants on the right, along with a metric ruler for scale. This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Raisin varieties depend on the type of grape and appear in a variety of sizes and colors including green, black, brown, purple, blue, and yellow. 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 small, sometimes seedless raisins that are much darker and have a tart, tangy flavor.

Drying raisins at Gata de Gorgos, Video by Valencian Museum of Ethnology. 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. Pre-treatment is a necessary step in raisin production to ensure the increased rate of water removal during the drying process. A faster water removal rate decreases the rate of browning and helps to produce more desirable raisins.

Recently, new methods have been developed such as exposing the grapes to oil emulsions or dilute alkaline solutions. These methods can encourage water transfer to the outer surface of grapes which helps to increase the efficiency of the drying process. Percentages are roughly approximated using US recommendations for adults. The three types of drying methods are: sun drying, shade drying, and mechanical drying. 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. After the drying process is complete, raisins are sent to processing plants where they are cleaned with water to remove any foreign objects that may have become embedded during the drying process. Stems and off-grade raisins are also removed. All steps in the production of raisins are very important in determining the quality of raisins.