Analysis of Acoustic Impulse Method for Determining Firmness and other Quality Parameters of 'Gloster' Apple

摘要

A comparative study regarding standard fruit quality measurements (fruit mass, firmness, soluble solids concentration, starch conversion rate and Streif index) and acoustic properties (resonant frequency, peak width, resonant frequency/peak width ratio and stiffness) were conducted in a??Glostera?? apples during two seasons. The findings obtained indicate no significant differences between seasons in studied quality parameters as well as in acoustic properties. The fruits were characterized with unusual high mass and high variation in resonant frequency and peak width, especially in season-I. In about 50% of examined fruit, the acoustic signal was not typical with one clearly visible peak, and appeared with two or, in few cases, even three peaks that were sometimes of similar height. The fruit mass was negatively correlated with resonant frequency, but correlation coefficient was lower in season-I and less significant than in season-II. Correlation coefficient between fruit mass and peak width was the same in both seasons. Although positive correlation existed between fruit mass and resonant frequency/peak ratio in both seasons, correlation coefficient in season-I was higher and more significant than in season-II. Correlation between fruit mass and stiff ness existed only in season-II. Resonant frequency was positively correlated with peak width only in season-I. Stiff ness was positively correlated with Streif index and peak width only in season-II. Though not significant, higher variations in acoustic properties than standard quality measurements still indicate some usefulness of acoustic impulse method for determination of fruit quality of a??Glostera?? apple. However, further research is needed to elucidate the significance of individual acoustic parameters and their relation to fruit quality.