Abstract
Nondestructive internal quality measurement by acoustic impulse response method was examined. Using apples and watermelons, several forms of the acoustic indices were compared with the results of constant speed uniaxial compression tests with cylindrical flesh specimens and sensory ratings. It was found that there were highly significant correlations among acoustic indices, apparent Young′s modulus (E'app), breaking stress and sensory firmness.
There were not any significant differences in the internal textural qualities of apples among ripeness classes which were evaluated by external appearance by experts of the fruits. Therefore, it is concluded that this nondestructive method has the advantage of being capable of evaluating internal textural qualities which are difficult to evaluate from external appearance.
The improved method of measuring flesh firmness by means of constant speed uniaxial compression test instead of hand-operated puncture testers has a good effect on the correlation between the acoustic indices and flesh firmness.
For apples, the indices which have more compensation for density than previously proposed indices gave increased correlation coefficients with internal textural qualities.
This acoustic impulse response method can be used as a nondestructive internal quality evaluation instead of the mechanical resonance method. The simplicity of this method is of great advantage to practical use.
