Judul: Studies on electrical impedance spectroscopy as a nondestructive quality evaluation of Garut citrus fruit
Abstrak: Garut citrus fruit is a local agriculture commodity, which have the opportunity to developed as a superior agriculture product. The productivity and quality of this product should be increased in order to meet market demand. Commonly quality of this fruit is evaluated by visual judgement ratio subject to error. This method also only evaluated the external quality of fruit. Internal quality of this fruit such as sugar content is determined by refractometer that is belong to a destructive method, and is not suitable for online quality measurement. So an objective and nondestructive method is required to evaluate quality of Garut citrus fruit. In this research, the potential of electrical impedance spectroscopy to determine quality of Garut citrus fruit was investigated. The electrical properties of Garut citrus have been investigated on frequency variation from 50 Hz to 5MHz. The fruits are placed between two plate electrodes, and treated as dielectric material. The study was conducted in four stages. The first stage is a study of the electrical circuit modeling to represent the electrical properties of citrus. This step is performed as an initial step study of the electrical properties of citrus fruit as nondestructive method for quality evaluation. Electrical models of citrus fruit constructed from circuit of resistors and capacitors. The electric models are built on the series and parallel configurations were adopted from the literature. Orange model development has also been carried out based on the internal structure of the fruit. Simulation and measurement results on citrus fruit shows a good match for certain values of resistors and capacitors. The correlation between measured data and simulations has been done by regression techniques. The best result is shown by the high value of the coefficient deterministic. Best correlation occurs in the new model. Changes in physicochemical properties during fruit maturation made changes in the value of the resistor and capacitor internal parameters of the model. If the pH increases, the capacitance value increases while the resistance value decreases. Changes in hardness and electrical resistance of the component models show a positive relationship, although not linearly correlated. However, an increase in hardness values correlate with a reduction in electrical capacitance value of the component in the model. In the second stage, Garut Orange fruit was assessed on its electrical properties associated with the spectrum or frequency variation of electrical signal. All electrical parameters divided by the amount of compensation parameters i.e. weight, volume and diameter of the fruit. The measurement results showed that the electrical impedance, resistance, reactance, capacitance, inductance per weight, per volume, and per diameter showed a similar phenomenon. Electrical impedance, resistance, reactance, capacitance, inductance per weight, per volume, and per diameter of citrus fruits will decrease if the frequency is increased. Citrus fruits, in general, are a weak electrical conductor, especially at low frequencies. However, when the frequency increased the ability of the electrical conductivity is relatively increased. Results in the second stage are used as the reference data to validate the model in the first stage. The third stage is the study of Garut citrus fruit quality based on physico-chemical
Keyword: