Detection of Fruit Firmness by Frequency Analysis

Abstract

High-value fresh agricultural products must maintain high quality standards and a predetermined shelf-life. Dynamic excitation and response sensing is an accepted method for the evaluation of fruits physical properties, quality, and shelf life. The purpose of the present study was to develop and evaluate a new nondestructive measuring technique of fruit firmness. The technique was based on mechanical impulse excitation, flexible piezoelectric film sensors and an FFT signal analysis method which was used to obtain the fruits resonance frequencies. Experiments with different geometrical configurations of the sensing elements, fruit mass, and impulse location were tested on three apple varieties. Results showed the potential of the new method to detect fruit firmness. 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 analysis by individual item are needed in order to develop reliable classification 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.