Species Identification of Food Contaminating Beetles by Recognizing Patterns in Microscopic Images of Elytra Fragments

PLoS One. 2016 Jun 24;11(6):e0157940. doi: 10.1371/journal.pone.0157940. eCollection 2016.

Abstract

A crucial step of food contamination inspection is identifying the species of beetle fragments found in the sample, since the presence of some storage beetles is a good indicator of insanitation or potential food safety hazards. The current pratice, visual examination by human analysts, is time consuming and requires several years of experience. Here we developed a species identification algorithm which utilizes images of microscopic elytra fragments. The elytra, or hardened forewings, occupy a large portion of the body, and contain distinctive patterns. In addition, elytra fragments are more commonly recovered from processed food products than other body parts due to their hardness. As a preliminary effort, we chose 15 storage product beetle species frequently detected in food inspection. The elytra were then separated from the specimens and imaged under a microscope. Both global and local characteristics were quantified and used as feature inputs to artificial neural networks for species classification. With leave-one-out cross validation, we achieved overall accuracy of 80% through the proposed global and local features, which indicates that our proposed features could differentiate these species. Through examining the overall and per species accuracies, we further demonstrated that the local features are better suited than the global features for species identification. Future work will include robust testing with more beetle species and algorithm refinement for a higher accuracy.

Grants and funding

SIP and HB are grateful to the National Center for Toxicological Research (NCTR) of U.S. Food and Drug Administration (FDA) for the summer research internship program and postdoc research program, respectively, through the Oak Ridge Institute for Science and Education (ORISE). This research was supported in part by internal grants from the FDA’s Office for Regulatory Affairs (to HD, Project IR01048) and NCTR (to JX, Protocol E0759101). The views presented in this article do not necessarily reflect those of the FDA. This research was conducted while SIP was a graduate student at Texas A&M University. The funders or SIP’s current affiliation (Samsung Austin Semiconductor, LLC) had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the “Author Contributions” section.