DETECTION OF FRUIT FIRMNESS BY FREQUENCY-ANALYSIS

High-value fresh agricultural products must maintain high quality stan dards and a predetermined shelf-life. Dynamic excitation and response sensing is an accepted method for the evaluation of fruit's physical p roperties, quality and shelf life. The purpose of the present study wa s to develop and evaluate a new nondestructive measuring technique of fruit firmness. The technique was based on mechanical impulse excitati on, flexible piezoelectric film sensors and an FFT signal analysis met hod which was used to obtain the fruit's resonance frequencies. Experi ments with different geometrical configurations of the sensing element s, fruit mass, and impulse location were tested on three apple varieti es. Results showed the potential of the new method to detect fruit fir mness. The findings confirmed previous works on acoustical response of fruits and vegetables. The measuring technique was found to be simple , fast, and repeatable. Additional tests of large sample size and anal ysis by individual item are needed in order to develop reliable classi fication algorithms for various fruit species. Due to its simplicity, applications of the new technique may include on-line determination of firmness and shelf-life of fruit and vegetables.