Place ricotta cheese in strainer. Drain for about 1 hour, or until most of liquid has been discarded.
Combine ricotta, sugar, flour, lemon juice, salt, egg yolks, evaporated milk, and milk in a large bowl; mix well.
In a separate bowl, beat egg whites until firm. Fold into batter until smooth. Divide filling into pie crusts.
Bake pies for 15 minutes at 425 degrees F (220 degrees C). Reduce oven to 350 degrees F (175 degrees C), and bake for an additional 25 minutes or until a knife inserted in the center comes out clean. Cool on wire racks. Refrigerate.
