Most raisins produced in the United States are made from seven different types of grapes: Thompson Seedless (which are also the most popular green grapes for fresh consumption), Flame Seedless, Muscat, Sultana, and Black Corinth. It takes about 4 1/2 pounds of fresh grapes to make 1 pound of raisins.
Flame Seedless raisins: These come from the Flame Seedless red grape and are large, dark red, and extra sweet.
Golden Seedless raisins: Like natural seedless raisins, these are also from Thompson Seedless grapes, but are oven-dried to avoid the darkening effect of sunlight. They are also treated with sulfur dioxide to preserve their light color.
Monukka raisins: These large, dark, seedless raisins come from the black grapes of the same name. They’re produced in limited quantities and are mostly available at health-food stores.
Muscat raisins: Large, brown, and particularly fruity-tasting, these raisins are made from big, greenish-gold Muscat grapes. Since the grapes contain seeds, the raisins are seeded mechanically, or are sold with seeds. Muscats are considered a specialty item and are mostly used in baking.
Natural seedless raisins: These are sun-dried Thompson Seedless grapes. They account for almost all California raisins. The green grapes naturally develop a dark brown color as they dry in the sun, a process that takes from two to three weeks.
Sultanas: These raisins, from the large, yellow-green Sultana grapes, are particularly tart and soft. They can be purchased in gourmet shops and health-food stores.
How to choose the best raisins
Boxes and bags of natural and golden raisins are available year round. Muscat raisins, preferred for holiday baking, are usually sold only in the autumn and winter months. Currants may only be found in specialty markets and larger supermarkets. Clusters of raisins still attached to the stem are sometimes displayed in specialty food stores.
When buying packaged raisins or currants, be sure that the box or bag is tightly sealed. Squeeze or shake the package to see if the fruit is soft. If the raisins rattle inside, they are dried out. When buying raisins in bulk at a gourmet shop or health food store, choose moist-looking, clean fruit. Don’t buy raisins from uncovered bins.
How to store raisins
Unopened packages of raisins will keep almost indefinitely in the refrigerator. Once opened, reseal the package, excluding as much air as possible, or transfer the raisins to an airtight jar or bag. Proper storage will deter the fruit from drying out and will prevent its sugar from crystallizing on the surface. If refrigerated, the raisins will keep for up to a year. They will stay even longer in the freezer and will thaw quickly at room temperature.