In the jar of a blender, combine 3/4 cup reserved pear juice with the orange juice concentrate, mustard, salt and pepper. Blend briefly and then, with the motor running, add the oil gradually, in a slow steady stream until the dressing is emulsified.
In a large bowl, toss the lettuce, cabbage, carrots and pears together. Pour the dressing over top and toss again, to coat all of the ingredients. Sprinkle the peanuts on top and toss again just before serving.