Original papersLow-frequency characterisation of mesocarp electrical conductivity in different varieties of olives (Olea europaea L.)

- An AC of 50 Hz was found to be suitable for characterizing the MI of olives.
- An ADC of 10 bits was sufficient for measuring the conductivity properly.
- The conductivity increased while the hardness decreased during maturation.
- Olive varieties have an average value of conductivity from ripening to maturation.
- Electrical conductivity can be easily applied in the olive groves.

Measurement of the electrical conductivity of various agrifood products is used to determine different parameters of foods, such as the moisture content and germinability of seeds or the resistance of fruits to frost. Recent studies have established the measurement of electrical impedance as a technique for assessing the maturity stage and fruit quality. In this study, we developed an experimental conductivity meter of alternating current (AC) at 50 Hz frequency, controlled by a microprocessor PIC18F2550 linked to a PC via a USB port. This device was used to measure the electrical conductivity in the mesocarp of olives (Olea europaea L.), which are used in oil production, at different stages of maturity. The measurements of electrical conductivity (expressed in % of full scale) were then used to establish an objective fruit maturity index and to determine the optimal timing of collection based on parameters such as oil yield and quality. The evolution of electrical conductivity in the mesocarp of the fruit was measured in four different cultivars, 'Picual', 'Manzanilla de Sevilla', 'Hojiblanca', and 'Gordal Sevillana'. Our findings showed that the conductivity increased according to the stage of ripeness. Similarly, each variety had a characteristic average value for the latter stages of ripening and maturation.