The minimization of the induced mechanical vibrations is a challenging and important problem in robotics. This paper presents two optimization approaches for smooth motion planning in redundant manipulators. The proposed strategies minimize the jerk of the robot end-effector by exploiting the structural redundancy of the manipulator and the functional redundancy of the desired task. Both the position of a selected redundant joint of the robot and one angle of the end-effector orientation are considered as optimization variables for each of the way points of the path to obtain a smooth motion. The approaches are verified on a manipulator with seven degrees of freedom performing a pick-and-place task. The results of extensive numerical tests demonstrate the performance of the proposed strategies in reducing the jerk of the end-effector with respect to a reference case.