ACOUSTIC TESTING OF AVOCADO FOR FRUIT RIPENESS EVALUATION

An acoustic method far nondestructive testing of avocado fruits was de veloped in order to determine the fruits' firmness index, internal dam ping and the centeroid of the frequency response. The method is based on mechanical impulse excitation and flexible piezoelectric sensors. E mphasis was made on the engineering aspects of the method. The effects of the fruits' irregular shape on the consistency and the variability of the rest results were examined. A comparison was made between the acoustic tests and destructive penetration tests during storage. The d amping ratio, which indicates fruit ripeness, increased monotonically with storage time, while the resonant frequencies and the firmness ind ex decreased with time. A correlation coefficient R = 0.659 to 0.806 w as found between the acoustic parameters and the maximum penetration f orce. A method is suggested to construct a ripening curve of fruits ac cording to their ''biological age''.