MELON RIPENESS MONITORING BY A PORTABLE FIRMNESS TESTER

A portable firmness tester for melons was developed. It measures the t ransmission velocity of an impulse waveform induced by an impact of a plunger on a melon. The pistol-shaped tester has a light-touch impact mechanism and two microphone sensors. Acoustic signals are transmitted to a computer through a PC card-type A/D converter: The transmission velocity calculated from the cross correlation of the two acoustic sig nals showed a high level of correlation (R = 0.94) with apparent elast icity measured from destructive tests. Measurements with the firmness tester can be used to monitor physiological changes in ripening melons .