Interactions of isolation and shading on ability to use fluorescence imaging to detect fecal contaminated spinach

Authors: Lefcourt, Alan; SIEMANS, MARK - University Of Arizona

Submitted to: Applied Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/10/2017
Publication Date: 10/12/2017
Citation: Lefcourt, A.M., Siemans, M. 2017. Interactions of isolation and shading on ability to use fluorescence imaging to detect fecal contaminated spinach. Applied Sciences. 7(10):1041.

Interpretive Summary: Produce presents a particular problem for food safety as most produce is eaten raw, with no kill step such as cooking or pasteurization. The primary source of most pathogens that cause foodborne illnesses are fecal materials. One step used to mitigate the risk of foodborn illnesses due to consumption of produce is to survey fields prior to harvest for fecal materials. Areas with identified problems are not harvested. This study examined the possible used of a fluorescence imaging system to enhance these surveys. A major problem with using fluorescence responses to ultraviolet or violet illumination is that responses are masked by sun light. A platform and drapes were used to try shade the area being imaged. Tests were made near solar noon, at dusk, and in the evening. Results showed that dairy manure place on a spinach leaf could be detected at dusk and at night. Detection at noon was problematic. It was suggested that a viable, relatively inexpensive, commercial system for detecting fecal materials in produce fields could be developed using fluorescence imaging techniques if fields were surveyed at dawn or dusk, or at night. This requirement is not particularly onerous as growers commonly conduct operations at night. This manuscript will be of interest to scientists concerned with produce food safety issues, to equipment manufactures interested in building field survey systems, and to produce growers and processors.

Technical Abstract: for evidence of fecal contamination. It may be possible to increase the efficacy of such surveys using imaging techniques that relay on detection of fluorescence responses of fecal material to UV excitation. However, fluorescence responses are easily masked by ambient illumination. This study investigated the potential of using a shroud to reduce the impact of ambient illumination on responses measured using relatively inexpensive optical components. During periods of near peak insolation, even with full shrouding, reliable detection would be problematic. Towards dusk, effective imaging could be accomplished even with a gap of 25 mm at the bottom of the shroud. Results suggest that imaging using relatively inexpensive components could provide the basis for detection of fecal contamination in produce fields if surveys were conducted during dawn or dusk, or at night.