Tristimulus mathematical treatment application for monitoring fungi infestation evolution in melon using the electrical response of carbon nanostructure-polymer composite based sensors

This work reports the study of the application of simple chemical sensors based on carbon nanostructure composite thin films for the detection of Fusarium sp., Drechslera sp., Aspergillus sp. section Nigri and Aspergillus sp. section Circumdati fungi present in melons (Cucumis melo Naudin). The responses of chemical sensor conductance G and capacitance C at 27 kHz were measured and used to calculate their ΔG and ΔC variations for melons during the ripening process under shelve conditions with intentionally promoted proliferation of Fusarium sp., Drechslera sp., Aspergillus sp. section Nigri and Aspergillus sp. section Circumdati fungus. These fungi are known to be frequent agents of occurring rot of melon during storage. Its early detection allows a relevant increase in shelf life, and in situ monitoring of fungal infections represents a very efficient tool to improve storage quality. The sensors response showed that the presence of fungi in melons can be electronically identified during the ripening process. We applied a method analogous to that used in colorimetry, the construction of the tristimulus space, to calculate the coordinates that can be univocally represented in a bidimensional graph, characterizing the sample. We show that the coordinate sequence constitutes a path evolving from the uninfected fruit to the fungi-only coordinates in a 20 days sequence of measurements after fungi inoculation.