Preheat oven to 350º F. (175º C.) In a small bowl, thoroughly whisk together soy sauce, vegetable oil, Worcestershire sauce, lemon juice, brown sugar, and ketchup (optional Dijon mustard).
Place pork chops in a medium baking dish, and spread with half the sauce.
Bake pork chops 30 minutes in the preheated oven. Turn, and spread with remaining sauce. Continue baking 30 minutes, or until internal temperature of the chops has reached 160º F.
(70º C.)
Variation, 24 April 2003: add 1 Tbsp. Dijon mustard to sauce and whisk as usual.