Non-contact and non-destructive firmness assessment of a mango fruit using laser-induced plasma impulse excitation.

Abstract

Many methods to assess a ripeness of fruit have been studied because its grades add further value in the marketplace. The ripeness correlates a firmness of fruit in general. A vibration testing using a shaker, a pendulum, a hammer, etc. evaluates the firmness of fruit during natural frequency measurements of 0S2 mode. The authors have developed the assessment method based on non-contact and non-destructive excitation force generated by laser-induced plasma shock wave, preventing damage by hitting the contact excitation devices to fruit. However, it might be hard to measure the ₀S₂ mode of fruit that is soft one such as mango. In this paper, we assess the firmness of a soft mango measuring a propagation velocity of Rayleigh wave on a fruit skin. Furthermore, we elucidate that the propagation velocity of Rayleigh wave decreases as their storage time increases.