Detection of internal quality in seedless watermelon by acoustic impulse response

Recent commercialisation of seedless watermelon varieties relies on the guarantee of a high quality product. Several internal defects may deteriorate greatly this fruit: (a) creases and/or large voids in the flesh, (b) overripeness and (c) bruises due to impact. The objective of this research was to develop a feasible non-destructive procedure for detecting these defects in individual fruits, based on acoustic impulse response. A device consisting of a microphone, structural elements and a mechanical impact generator was designed and tested. Good and defective seedless watermelons were tested with the acoustic device. Spectral parameters were examined as potential non-destructive predictors of internal disorders. Waveband magnitude parameters, obtained by summing the magnitude of the spectrum between two frequencies in a specified band width (always including between 40 and 500 Hz), were the acoustic parameters showing the best ability to detect internal disorders. (C) 2004 Silsoe Research Institute. All rights reserved Published by Elsevier Ltd.