Sift flour and ginger into a bowl, and stir in sugar. Combine molasses, margarine, and egg white; stir well. Add to dry ingredients; stir until well-blended. Cover and place in freezer 30 minutes or until firm. Shape dough into 18 (1 1/4-inch) balls; place 1 inch apart on a baking sheet coated with cooking spray. Bake at 350° for 12 minutes. Remove from pan; let cool on a wire rack.