Raisin juice is a concentrated raisin extract. It is produced by soaking raisins in water to leach a variety of compounds out of them, and then evaporating the resulting liquid to create a concentrated juice. There are a range of uses for this extract, many of which are commercial in nature, although some people use it in home cooking or as a dietary supplement. Raisin juice can be purchased in large quantities from companies which supply commercial confectioners, and it can also be found in smaller amounts at health food stores and some markets.
The concept of raisin juice might seem a bit odd, since raisins are, after all, dried grapes, and grape juice is an already well known substance. However, raisin juice is not the same thing as grape juice. Because raisins are dehydrated, their juice is in turn a highly concentrated substance, with less water than grape juice. It is also intensely sweet, as typically sweet varieties of grapes are used to make raisins, and their sugar content increases with dehydration.
One of the most common uses of raisin juice is as an all natural source of color in commercially produced baked goods, candies, and other foods. It is also a mild natural preservative, so companies which want to produce foods with natural products may use it, especially in breads. It is also used as a sugar substitute, taking advantage of its intense sweetness, and it can help to maintain moisture in baked goods, as well as acting as a binding agent.
In theory, raisin juice can also be consumed straight. It can be drizzled as a syrup on ice cream and baked goods, or taken as a standalone supplement. It contains high amounts of thiamine, niacin, folate, vitamin B6, and vitamin B12, among other dietary minerals. Home cooks can also take advantage of its natural sweetness and preservative abilities in foods, especially things like cookies which they might want to ship to distant locations.
The color of raisin juice varies from amber to dark brown, and it can be thick to thin, depending on how long it is evaporated. Because it is a natural preservative, the juice should last for an extended period of time when kept under the right conditions; a cool, dry place with no light is ideal.