In the northern hemisphere harvesting of sultanas and raisins is during September and October. The grapes are manually picked, the same as for the wine production. Then they are passed on for drying. This process is decisive for the look of the fruit.
There are light− and dark coloured sultanas. The sultanas’ colour however has nothing to do with the colour of the fresh grapes. All sultanas, also the dark, originate from green grapes. Different colours result from varying drying methods.
In ancient times the grapes were simply spread out for drying in the sunshine. After 2 − 3 weeks the grapes were dry and had turned dark−brown to black in colour (this method is still used for currants and Californian sultanas).
The Greek discovered a new method halving drying time and enlightening the colour of the dried sultanas. Before drying the grapes were dipped into a solution of flavoured oil and potash resulting in the following.
The berries are covered by a layer of overlapping scales like roof tiles. The solution of olive oil and potash cause the scales to prop up. By this proceedure the drying time is 2 − 3 times quicker.
The quicker the grapes are dried, the less is the enzymatic effect leading to the unwanted dark discoloration of the sultanas. Besides the sultanas remain soft and keep the full flavour.
The fruit can additionally be treated with sulphur dioxyde to obtain an even lighter colour. The sultanas will turn golden−yellow.
Iran also has green sultanas. This untreated variety is dried in the shade, but the drying time is twice as long as in the sun, meaning up to 6 weeks. By drying in the shade the greenish colour is maintained.
Nutritive value per 100 g sultanas / raisins
number of berries per 100 g.:
Normalberried: 300 − 350
Smallberried: 500 − 600