Partially dried fruits have the advantages of long shelf life and reduced bulk. Care must be taken to seal well when not in use, as the fruit can go dry and hard when exposed to air.
Raisins are the dominant partially dried fruit in baking and are used in:
- Pies and squares
- Bread and buns
- Cakes and pastries
Raisin is the commercial name given to sun-dried or mechanically dried grapes. Drying reduces the moisture content, simultaneously resulting in increased sugar content. It is the greater sugar content that preserves the fruit against bacterial attack.
The United States accounts for about one-third of the world’s raisin production, heavily centred in the San Joaquim Valley in California. Well over 90% of these are the Thompson seedless variety.
Dark raisins are dried in the sun over a period of 8 to 14 days. Golden raisins undergo a different process and are never allowed to dry in the sun. The steps for golden raisins are:
- Dipping in caustic solution to remove the waxy bloom and cause cracks to form, speeding up the escape of moisture
- Washing to remove the caustic solution
- Travelling through ovens where sulphur dioxide treatment preserves the colour
- Going through a final oven drying to complete drying
- Inspecting and fumigating to prevent insect infestation
There are two methods of conditioning raisins:
- They are soaked in tepid water at about 27°C (80°F) for five minutes, and then drained for one hour
- They are covered with water at about 27°C (80°F) and immediately drained without soaking. They are then set aside, covered, and left for a few hours. The raisins will slowly take up the moisture.
The second method is preferred because no sugar is lost from the fruit. In both cases, there is a moisture gain of about 10%. Bakers may choose to condition batches of raisins sufficient for a few days’ or a week’s supply.
Raisin Varieties Used in Bakeries
There are four main varieties of raisins used in bakeries:
- Thompson: Seedless, thin-skinned, and available in suntan or golden yellow colour, they are a popular ingredient in the production of light fruitcakes.
- Sultanas: A lot like Thompson raisins except, but these are round in shape and have a trace of small edible seeds. They are firm with a tart flavour and are used in breads, buns, cakes, puddings, mincemeat, etc.
- Currants: Originating in Greece where they are called the “raisin of Corinth,” these raisins are now grown in California as the Black Zante currant. Currants are very small seedless raisins and have a very tangy flavour that is different from other raisins. (They are occasionally confused with black currants, which are a different berry, also with a tart flavour.) Bakers use them in buns, fruitcakes, and puddings.
- Muscats: Called “Muscat of Alexandria,” they were brought to California from Egypt in 1851. They are very large with a high sugar content and are famous for their flavour. They are sold as regular muscats or seeded muscats in which the seeds have been removed with special machines. They mush easily, don’t hold their shape well, and are therefore not well suited for use in bread and buns but are excellent for use in pie fillings, mincemeat, and puddings.
Natural raisins packed in bulk fibre cases can be stored for several months at room temperature without any noticeable loss in flavour or colour if protected against insects. The humidity level (ideally relative humidity of 50%) is important and the raisins should be sealed well between uses. If the humidity increases too much, raisins will start to “sugar”; that is, sugar crystals will develop on the exterior surface (similar to the sugar bloom on chocolate candies). This does not mean that the fruit is unusable.
Apart from raisins, other dried fruits are widely available and can be treated and used in much the same way.