Combine yeast, 1 teaspoon sugar, and warm water in a mixing bowl; stir well. Let stand 5 minutes or until bubbly.
Combine milk, shortening, salt, and remaining sugar; stir until shortening is melted. Add cooled milk mixture to yeast mixture; stir well. Beat egg whites (at room temperature) until stiff peaks form; fold into yeast mixture.
Gradually add 6 cups flour, stirring until dough leaves sides of bowl. Shape into a ball, and place in a greased bowl, turning to grease top. Cover and let rise in a warm place (85°), free from drafts, 1 hour or until doubled in bulk. Punch dough down, and turn out onto a lightly floured surface. Let dough rest 5 minutes.
Knead remaining flour into dough. Shape into a ball; place in a greased bowl. Cover and repeat rising procedure 1 hour or until doubled in bulk.
Punch dough down; turn out onto a lightly floured surface, and knead 4 to 5 times. Let dough rest 5 minutes.
Divide dough in half, shaping each into a loaf. Place in 2 greased 9- x 5- x 3-inch loaf pans. Cover and repeat rising procedure 30 minutes. Bake at 350° for 35 minutes or until loaves sound hollow when tapped. Remove bread from pans immediately; cool on wire racks.