Thompson seedless raisins and Sultanas

Thompson seedless raisins, unlike currants which are peculiar to Greece, can be obtained from a number of different countries, principal of which are USA, Turkey, Chile, South Africa and Iran. The USA is the largest producer and there is no doubt that the quality of their fruit is very good. Most US raisins are "naturals", that is, sun-dried and processed without chemical treatment, giving a dark coloured fruit. There is a small proportion of sulphur dioxide bleached grapes which are artificially dried and these produce golden raisins which are like sultanas from other countries.

Smyrna sultanas are directly related to Thompson seedless raisins and these represent a significant and very ancient trade from Turkey and Greece (principally the island of Crete). Australia and Iran are also significant producers and exporters of sultanas.

Both raisins and sultanas are always larger and more fleshy than currants and therefore less suitable for biscuit making. When a fleshy fruit is dried out during baking it becomes tough and leathery, maybe even hard and bitter if on the surface of the product.

Traditionally bunches of sultana grapes are dipped in a solution of potassium carbonate emulsified with a little olive oil before being laid on a compacted earth bed to be dried in the sun. This treatment removes the bloom on the grape surface, softens the skin and hastens the drying. The sultana is dried till it starts to darken, a pale sultana is prized so over-drying is avoided. The dipping prior to drying also reduces the tendency to darken, hence the difference from Thompson seedless "naturals".

Eventually the fruit arrives at the packing factory. Here it is washed, spin dried, picked and graded. Grading of sultanas and Thompson seedless raisins is based on screen size, colour and counts of defects and foreign matter.