Preheat oven to 450˚F (230˚C). Line baking sheet with parchment paper. Set aside.
Add vinegar to saucepan of boiling water. Blanch sweet potatoes 3 min. Drain and cool. Toss with cornstarch then dip in egg whites to moisten all sides. Arrange on baking sheet. Sprinkle with salt.
Bake 20 to 25 min. until lightly crispy on outside, tender inside.
Oven-baked fries offer lower fat and calories than deep-fried ones. Plus, sweet potatoes deliver higher levels of vitamin A than white spuds.