quality analysis of pear fruit of shah miveh variety using nondestructive ultrasonic technique

development of ultrasound technique has not been progressing for evaluating the internal quality of fruits as fast as that of processed foods. in this research for quality assessment of pear fruit (shah miveh variety) an ultrasonic measurement system was constructed to transmit and receive the ultrasonic waves. the apparatus included a pulser-receiver, a pair of 75 khz ultrasonic transducers with exponential horn, and a computer system for data acquisition and analysis. several mechanical and chemical properties, including firmness, tss, acidity, elastic modulus, ph and total dry matter for destructive quality assessment were measured. velocity and attenuation of ultrasonic waves for nondestructive tests were also measured. the fruit quality levels for the experiment were: unripe, ripe and overripe. the results of tests showed that firmness was the best parameter for measuring fruit quality, as it decreased significantly with ripeness. the effect of ripeness on the velocity and attenuation of ultrasonic waves was also significant. investigation showed a positive linear relationship between fruit firmness and wave velocity (r2=0.81). furthermore, the relationship between fruit firmness and attenuation was exponential and wave attenuation decreased with increasing fruit firmness (r2=0.895). the relationship between ultrasonic properties and fruit modulus of elasticity showed that the wave velocity increased and attenuation decreased with increasing elasticity. it can be concluded that the ultrasonic instrument equipped with exponential horns can effectively be utilized for pear quality assessment based on measurement of wave velocity and attenuation.