Preheat oven to 200 degrees C. Grease muffin cups or line with patty cups.
In a large bowl, sift together flour, baking powder, salt and sugar. In a separate bowl, combine egg, orange rind, orange juice, milk and vegetable oil. Stir egg mixture into flour mixture just until moistened; fold in sultanas. Spoon batter into prepared muffin cups.
Bake in preheated oven for 20 to 25 minutes, until a toothpick inserted into centre of a muffin comes out clean.