Nondestructive Detection of Hollow Heart in Potatoes Using Ultrasonics

Abstract

Ultrasonic techniques were used to detect hollow heart in potatoes nondestructively. Fifty Russet Burbank potatoes were evaluated physically and sonically. A pair of dry-coupling 50-kHz ultrasonic transducers were used to generate an ultrasonic pulse with a power level of 0.22 W for the test of acoustic transmission through whole potato tuber in a transverse direction at different locations along the longitudinal axis with a certain interval distance. It was found that the waveform analyses in time domain for a series of transmitted signals along the longitudinal axis of potato tuber, yielded the potential in detecting hollow heart in potatoes noninvasively. The transmission losses for potatoes having hollow heart were found to be greater than 0.28 dB/mm. This value was used as a criterion to indicate potatoes with hollow heart at an accuracy of 98 percent. The ability to detect hollow heart in potatoes was limited to a minimum cavity size of 0.5 cm3 because the interval distance between locations of measurement was relatively large compared to the size of the projected area of hollow heart. The accuracy of the detection would be improved if a smaller contact area for the transmitting transducer were used, and if the intervals between ultrasonic measurement locations were smaller. Physical properties of the tested potatoes were also recorded for consideration of their relationships with ultrasonic parameters. Physical properties of tested potatoes such as modulus of elasticity, tuber length, diameter, and weight, were found to have poor correlation with ultrasonic parameters such as ultrasonic velocity, attenuation coefficient, and root mean square voltage of transmitted signal. This study showed that if all potatoes with weights of 300 g or less were eliminated from a mass of incoming potatoes, only 80 percent of the total mass would have to be examined for hollow heart.