Rapid detection of d-limonene emanating from citrus infestation by Bactrocera dorsalis (Hendel) using a developed gas-sensing system based on QCM sensors coated with ethyl cellulose

D-limonene is one of the main olefin gas compounds released from citrus and its relative content changes most obviously with the infection time of Bactrocera dorsalis (Hendel). Thus, it is necessary to detect D-limonene content released from citrus, which may lead to detect the presence of early infestation by B. dorsalis in citrus. In this study, a gas-sensing system based on quartz crystal microbalance (QCM) sensors coated with ethyl cellulose (EC) was developed to detect D-limonene aromas emanating from Australian citrus. There was a linear relationship between the frequency shift and D-limonene concentrations ranging from 60 mg m(-3) to 6000 mg m(-3) with a determination coefficient (R-2) of 0.9899, and the limit of detection for D-limonene in pure gas was 300 mg m(-3). It has also been observed that the QCM sensor has better selectivity towards D-limonene aroma. Additionally, the sensor was found to be repeatable with an average R value of 96.31 %, and the lifetime of the sensor can be extended at least to one month with an acceptable drift (3.40 %) in their sensing characteristics. Furthermore, it was confirmed that there was high consistency between the QCM sensor's response and the GC-MS for D-limonene aroma. The six VOCs contributing the most to differentiating citrus infested with B. dorsalis were identified. The gas-sensing system based on QCM sensors has potential feasibility for the rapid detection of the presence of B. dorsalis infestations in postharvest citrus.