In bowl, stir together flour, sugar, baking powder and orange rind. Whisk milk, eggs, butter and vanilla; stir into flour mixture just until blended. Fold in blueberries. Spoon into lightly greased muffin tins, filling three-quarters full. Bake in 200ºC (200 C) oven for 20 to 25 minutes or until golden and firm to the touch. Makes dozen muffins. Per muffin: about 165 calories, 4 g protein, 4 g fat, 28 g carbohydrate.