Coat a large nonstick skillet with cooking spray; add oil. Place over medium-high heat until hot. Add pork slices, and cook until browned on both sides, turning once. Drain and pat dry with paper towels. Set pork aside.
Coat skillet with cooking spray; place over medium-high heat until hot. Add apples; saute until tender. Add apple juice concentrate, and bring to a boil. Stir in mustard, salt, and pepper; add pork. Cook until thoroughly heated. Serve immediately.