A Feasibility Study of Employing a Capacitance Based Method in Banana Ripeness Recognition



Grading of agricultural products has always been a subject of research by scientists. One of the criteria to be chosen for grading of fruits is the fruit's level of ripeness. Different methods have been employed to assess the status of fruit ripeness some of which are destructive and others are not so. In this research, a noninvasive capacitive method was used to estimate the ripeness level in banana fruit. The relationship between levels of ripeness and dielectric constant were studied over the frequency range of 1 kHz to 10 MHz. Results revealed that the dielectric constant is severely influenced by the dimension and weight of the fruit. To eliminate the interfering effects of these parameters, a second model was proposed to predict the dielectric constant of banana fruit. This model is a function of equivalent dielectric constant, volume, effective length as well as width of the fruit. The dielectric constant showed a decrease with increase in the ripeness of the banana fruit. Since the decrease was more distinct at the 1 MHz, this frequency was employed to calibrate the system. The firmness was assessed also as a quality index and the relationship between dielectric constant and firmness also studied. The results of prediction were somehow acceptable with the correlation coefficient between the predicted vs. the real ripeness obtained as 0.853.