Electronic Olfactometric Discrimination of Lemon Contamination from Penicillium spp. during Storage

The most common and serious diseases which occur in Italy as well as in many other countries during storage and marketing of citrus fruit are green and blue moulds incited respectively by Penicillium digitatum and Penicillium italicum. These diseases can cause significant economic losses during storage and transport. Volatile compounds produced when fruit are spoiling represent a rapid and early indication of the upcoming deterioration. Thus it can be considered as a promising field of application for electronic nose technology as previously reported, where the instruments' sensibility was not tested. The objective of our research was to investigate the sensitivity of a quartz piezoelectric electronic nose (Merlino LibraNose, Technobiochip Italy) to detect low percentages of lemon infected with Penicillium digitatum among sound fruit. Sound and sound plus infected fruits were allocated respectively in two different plexiglas air isolated bins (control vs. infected bin). The percentages of infection utilized were 1 and 5%. The sound fruit used to fill the bins were previously treated with 1000 ppm of Imazalil to avoid mould spreading and the consecutive increasing of the percentage infected. Measures were carried out for four days after each percentage of infected lemon were inserted in the infected bin as well as in the control. The average value of 6 sensor signals of the infected samples, increased to 4.9% with respect to the control for the lower infection, reaching a value of 22.3% for the higher one (5%). Moreover, multivariate classification (PLS-DA) was able to discriminate with good performance between values regarding sound and infected fruits.