Non-destructive quality assay of different peach cultivars by photoacoustic method

Quality assay and caring of fruit and vegetables has basic role on modern agricultures today. Photoacoustics is a new method of non-destructive detection of the properties of biological materials, in which light energy is used to produce ultrasonic waves in various materials.The received ultrasound waveform contains useful information about the textural properties of the adsorbent medium. This research investigated and evaluated the quality of three peach cultivars during their storage period using non-destructive photoacoustic method in comparison with destructive penetration method. For this purpose, a system for ultrasound wave generation was implemented using laser pulse radiation with a wavelength of 1064 nm. The maximum amplitude of the photoacoustic signal and the time of occurrence of this amplitude were extracted from the experimental samples. Also, by separate penetration test, the amount of firmness and modulus of elasticity were measured on the same samples. By selecting the factors of peach cultivar, size and caring time, the obtained data were analyzed in a completely randomized experimental design with 5 replications. Finally, the means of the two sets of data obtained from the two tests were compared by examining the correlation coefficients. The results showed that in all sources of variables in the measurement indices except the size factor in the maximum signal index there is a significant difference between the averages of the indices at the level of 5%. Over time, the maximum signal amplitude index decreased. As the sample size increases, the maximum amplitude time value increases more. There was a significant difference between the two levels of care. There was an interaction between factor of peach cultivar and factor of caring time. The results showed that the modulus of elasticity decreased in larger sizes. Comparison of the means of peach cultivar factor in firmness index showed that there is a significant difference in all three levels. The highest amount was in Balkhi cultivar and the lowest amount was in Zafarani cultivar. The mechanism of the photoacoustic signal produced by laser radiation on the surface of the material depends on the mechanical properties of the irradiated material and the properties of the light source. Therefore, the change in signal amplitude is affected by the initial pressure wave caused by the laser radiation on the surface of texture. Based on the results, the time of occurrence of the maximum signal is a good indicator to assess the quality of peach fruit texture during its care period. The results of correlation between the data of the two tests showed that the highest correlation coefficient between texture of firmness and the maximum amplitude of the photoacoustic signal is for three cultivars. So that Balkhi cultivar had the highest correlation coefficient equal to 0.821. These results prove the validity of non-destructive and non-contact measurement methods in texture quality.