Assessment of avocado textural changes during ripening by using contactless air-coupled ultrasound

In the present study, the use of the air-coupled ultrasonic technique has been analysed as a new tool for the contactless assessment of the avocado post-harvest textural modifications during ripening. Thus, ultrasonic parameters, such as maximum wave amplitude and ultrasound velocity, and textural ones, such as hardness, elastic modulus and relaxation capacity, were measured on avocado slices. During ripening, avocado reduced its elastic modulus (from 2.29 ± 0.75 to 0.16 ± 0.08 MPa), became softer and became more viscoelastic, which was well described from zero and first-order kinetic models. These changes increased ultrasound attenuation, decreasing the maximum amplitude of the ultrasonic signal (from 336.6 to 55.4 V/m), while the ultrasonic velocity remained constant, between 320.1 ± 6.9 and 316.4 ± 82.6 m/s. Thereby, the maximum ultrasonic amplitude, which adequately correlated with textural parameters (ravg = 0.85), could be used to assess the post-harvest ripening on avocado slices. •Air-coupled ultrasound was used for contactless estimation of avocado texture.•During ripening, avocado reduced its elastic modulus and became more viscoelastic.•Textural parameters followed zero and first-order kinetic patterns during ripening.•Ultrasonic signal amplitude (At) decreased and the velocity remained constant during ripening.•At was well correlated with elastic modulus, hardness and relaxation capacity.