Drain crushed pineapple,set drained juice to the side for use in the icing. In a large bowl mix the drained pineapple, mandarin orange juice, milk, oil then add egg. In a separate bowl mix wheat flour and baking powder, once well mixed add to wet mixture. Fill greased muffin tins about 1/3 full and bake for 20 to 25 minutes or until the center springs back when touched.