In a small bowl, mix milk and lemon juice; set aside.
In a large bowl, combine flour, sugar, baking powder, cinnamon and salt. Set aside. Add egg and oil to milk mixture. Gently stir into flour mixture just until moistened. Fold in blueberries.
Fill greased or paper-lined muffin cups two-thirds full. Bake at 400° for 22-24 minutes or a toothpick inserted in the muffin comes out clean. Cool for 5 minutes before removing from pan to a wire rack to cool.