Abstract

The invention relates to non-destructive measurement of the firmness of fruits and vegetables, particularly to methods and equipment for measuring the firmness of such edible objects in order to establish their ripeness or maturity stage, not only after they have been harvested or stored, but also during the growing process. The method comprises:- 1) gripping the object in two substantially diametrical points between two gripper bodies at a predetermined pressure, 2) applying a vibrational excitation onto one of the two points by means of a vibration actuator using a composite signal with predetermined frequency content, amplitude range and phase shift configuration, specialized for the kind of fruit to be tested, 3) measuring the input signal by means of a first acceleration transducer attached to a gripper body on the vibration actuator contacting one side of said object 4) measuring the output signal on the other side of said object by means of a second acceleration transducer attached to an opposite gripper body, 5) passing the signals through a difference amplifier and obtaining a relative acceleration signal by deducting the input signal from the output signal, 6) feeding the obtained signals to computer means and obtaining a firmness index by the quotient of the root mean square of the output acceleration signal divided by the root mean square of the relative acceleration signal. The equipment may comprise manually or automatically operated table-top or hand-held "FIRMNESS TESTERS" or "FIRMNESS SENSORS" that can be mounted as robotics end-effectors or incorporated in a cup-conveyor line for automatically sorting fruits and vegetables by firmness, in a packinghouse.