Drying fruit, one of the oldest preservation techniques, derives from the discovery that fruit left to dry in the sun were still edible. Drying concentrates the sugar content in fruit, and, although it usually loses its vitamin C in the process, vitamin A and the minerals are still retained. Some fruit are still sun–dried, while others may be dried by mechanical means, and some are coated in sulphur dioxide to prevent them from drying out completely. Dried fruit is high in fibre, is a convenient snack food, and is often used in baking, for compotes or in stuffings for meat. The three main vine fruit, currants, raisins and sultanas, are all dried grapes. Currants are small black grapes; sultanas are dried, white grapes; and raisins vary according to the variety but are traditionally muscatel grapes. Vine fruit play an essential role in Christmas puddings, in cakes, biscuits, mincemeat, in couscous or stuffings and sauces. Dried peaches and pears make excellent snacks and dried apricots can be chopped and added to muesli, rice dishes and stuffings for chicken and lamb. Dried apricot is also sold rolled into sheets. Dried apples, which retain their Vitamin C when dried, are sold in rings or pieces. Many exotic fruit such as mango and papaya are also dried and these are best eaten as snacks. Prunes are eaten dried as a snack or plump them up by keeping them in brandy or another liquid, then add to stews, cakes or puddings. They go well with pork, lamb, poultry and game.