Assessment of fruit ripening through electrical impedance spectrometry.
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In this thesis, some of the different parameters that can determine fruit ripening have been measured and analyzed through non-destructive techniques by following the ripening process of three different kinds of fruits: mangoes, bananas and avocados. The parameters analyzed were the electrical impedance, electrical phase, weight and colour of the fruit.Therefore, the experimental measurements took all place in a room maintained at an average temperature of 20 degrees. The fruit was kept in this room at all times throughout the experimentation period, keeping it stable and avoiding external influences affecting the ripening parameters. The measurements were carried out every day at 13 pm for a period of 12 days. The electrical impedance was measured with an AD5933 board between the frequencies of 1kΩ and 100 kΩ. The weight was measured with a kitchen scale and the colour was evaluated through both the pictures and the Fiji software.Finally, the results showed that, in reference to the weight evolution, all of the three fruits follow a linear decreasing evolution, following similar mathematical slopes. In reference to the electrical impedance, the results showed that the impedance of mangoes increases when these fruits ripen, while the banana’s decreases. The evolution of the avocados impedance, however, follows an irregular behaviour. Moreover, the measurements showed that the angle stays constant during the ripening process and that there is not a huge or significant variation of colour composition throughout the ripening days.Finally, the relationship between the electrical impedance and the weight was analyzed, as well as the sensitivity of the electrodes.