Determination of peach maturity using ultrasonic waves

The tissue of fruit varies at different stages of growth and storage and by determining its characteristics; the stage of fruit maturity can be found. Depending on the type of tissue, the ultrasonic waves will attenuate and its speed will change too while crossing the fruit tissue. Thus, by calculating the attenuation coefficient value and its speed in no destructive way, the characteristics of fruit tissue and the rate of its maturity will be determined. In this study, peach fruits -the Tabrizi variety- were classified in ripen, semi-ripen, large and small groups and the validity of ripen and semi-ripen groups were confirmed by taste panel. Then, in addition to measuring the attenuation coefficient and velocity of ultrasonic wave parameters, the physic-chemical parameters of fruit, including dimensions, mass, density, hardness, reducing sugar, acidity, pH, dry weight and soluble solids contents, which are the maturity indices of peach, were measured and compared with ultrasonic parameters. Results showed that fruit size and degree of maturity significantly affect on the wave attenuation and wave velocity, respectively. The correlation coefficients between attenuation coefficient and hardness (without skin) in ripen and semi ripen groups were higher than 0.8 and also the correlation coefficients of attenuation coefficient in relation with the hardness (by skin) in ripen and semi ripen groups were higher than 0.7. Also, the correlations for both attenuation coefficient and wave velocity in relation with the pH were higher than 0.8 as well as correlation between wave velocity and acidity.