Using technology to defeat a tiny beetle which threatens grain stores

These inexpensive, disposable sensors, manufactured by iSense, are approximately one square inch in size (about the size of a postage stamp) and spotted with seventy-three dyes, which change color in response to various vapors which come in contact with the CSAs from the sample. Samples are identified, not by any single spot color change, but instead by the combination of color changes across multiple spots forming a “fingerprint” that can be used to identify compounds found in a sample.

The CSA color changes are sensitive enough to detect even trace amounts of some vapors (odors), allowing for the broad spectrum detection of a number of volatile organic compounds, or VOCs, which may be well below concentration levels attributable to health risks. A wide range of patterns or signatures, resulting from emitted VOCs, can be elucidated and stored for various compounds, creating a reference library for any previously recognized material.

During an assay, CSA sensors are exposed to odors emitted into the headspace above bulk grain infested with beetles. Over time, changes in the colored spot patterns emerge, and by using special software designed specifically for this project by Charles Davidson, Ph.D., unique color fingerprints are revealed.

The goal of the project is the development of unique and individual spot patterns capable of differentiating between invasive, quarantined khapra beetle infestation and other non-invasive species.

Detection of infestation is based on volatile signatures within a closed container — a method, which has the potential of allowing infested cargo to be sequestered before being opened, thereby mitigating exposure or release of the species within. With success, this technology could transition into a self-contained sampling and detection unit, which could wirelessly transmit results to a smart phone for analysis.

ECBC envisions a solution, where an inexpensive, disposable reader could be placed within a crate before shipment, then later queried by a smart phone to allow inspectors at the port of destination to assess food security and quality without ever having to open the container.

The first step in making this method a reality is the development of a reproducible signature library capable of differentiating between beetle-infested grain and pristine grain.

Since khapra beetles are a quarantined species, scientists began testing the CSAs using the common warehouse beetle, which is closely related to the khapra beetle. The team simulated the highly-infested environment of shipping containers by using grain-filled glass mason jars either with or without beetle contamination. The CSAs were placed in the jars and scanned at regular intervals to track color changes.

DOD notes that while the research is still in its infancy, researchers have been able to distinguish between the warehouse beetle-infested and non-infested grain based on the response of the CSAs to the VOCs present in the headspace above the grain. The information that has been gathered is foundational in moving the project closer to its goal of creating an inexpensive, disposable tool to query shipping containers, which will allow inspectors to assess food safety without ever opening the container. The group expects to complete its first round of testing by the fall of 2015.