Acoustic Impulse Response for Measuring the Firmness of Mandarin During Storage

The objective of this research was to evaluate the ability of acoustic impulse response for monitoring the mandarin firmness change during storage. The dominant resonant frequency, stiffness coefficient (SC) and elasticity coefficient (EC) decrease with storage time. A good correlation was established between the acoustic parameters (SC and EC) and fruit compression force, and the correlation coefficients were 0.88 and 0.92, respectively. Acoustic impulse response gives a good indication of firmness change for mandarin during storage. The change of EC was more prominent (greatest), and hence it can be a better index of mandarin firmness. The nondestructive acoustic test might replace conventional destructive test for mandarin to determine fruit firmness and expected shelf life.