Non-destructive determination of the optimum eating ripeness of pears and their texture measurements using acoustical vibration techniques

We investigated the time-course changes in the elasticity index (EI) and texture index (TI) of pears (Pyrus communis L. cv. La France) during the postharvest period. EI was determined using a formula EI=f22m2/3, where f2 is the pear sample's second resonance frequency and m is the sample mass. A non-destructive vibrational method using a laser Doppler vibrometer (LDV) was used to measure the pears' second resonance frequency (f2). Changes in the EI of the pears showed bi-phasic decay. Along with sensory testing, we determined the period of optimum eating ripeness of the pears in terms of their EI to be 8.1 × 104-1.5 × 105 kg2/3 Hz2. Pre-determined EI of pears enables consumers to predict the time range of optimum eating ripeness. An improved device for texture measurement was used for measuring time-course changes in the texture of pears. The texture was quantified with TI, which was determined for 18 frequency bands through integration of squared amplitudes of texture signals multiplied using a factor of a frequency band. The TI declined gradually over a wide frequency range as the pear samples ripened.