Preheat oven to 350. In a large bowl, mix oil, sugar, lemon extract, and egg whites. In another bowl, combine flour with baking powder. Add flour mixture to sugar mixture alternately with milk, stirring just until blended. Fold in blueberries and lemon rind. Pour batter into 9 by 5-inch loaf pan coated with non-stick cooking spray and dusted with flour. Bake 40-50 minutes or until toothpick inserted in center comes out clean.