A TRANSPORTABLE FLUORESCENCE IMAGING SYSTEM FOR DETECTING FECAL CONTAMINANTS

Authors: Lefcourt, Alan; Kim, Moon; Chen, Yud

Submitted to: Computers and Electronics in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/25/2005
Publication Date: 6/1/2005
Citation: Lefcourt, A.M., Kim, M.S., Chen, Y.R. 2005. A transportable flourescence imaging system for detection of fecal contaminants. Computer Electronics in Agriculture. 48:63-74.

Interpretive Summary: Animals feces are a common source of microorganisms that can cause illness or death. Contamination of foods and food products with these organisms is a critical health issue. Fortunately, feces normally contain chemical compounds such as chlorophyll that can be detected by the fluorescent responses of these compounds to ultraviolet light. This paper describes a transportable system that can be used to detect fecal contamination of foods and food products. The systems works by illuminating an object with ultraviolet light and looking for an inappropriate fluorescence response. The system primarily consists of an ultraviolet light source, a light-intensified camera with a six-position filter wheel, and computer software for controlling the system and automatically analyzing the resulting images. The hardiness of the system was demonstrated when the system was used successfully at a public field day to image apples artificially contaminated with dairy feces. The contamination sites were easily identified using automated detection methods. In addition, it is known that fecal contamination sites on apples can be identified using fluorescence imaging even after the apples are washed. By applying feces to apples and washing some of the apples at hourly intervals, it was determined that five hours was the minimum contact time that allowed identification of the contamination site after the apples were washed. This system can be used to study the effectiveness of apple washing systems. The technology may also provide a basis for developing tools to monitor the cleanliness of food preparation areas.

Technical Abstract: Feces are the ultimate source of many pathogenic organisms that can potentially contaminate agricultural commodities. Feces generally contain chlorophyll-a and related compounds due to ingestion of plant materials. Fluorescent responses of these compounds to appropriate excitation can mark the presence of feces on animal carcasses, or on fruits or vegetables. Described is a transportable imaging system for detecting fecal contamination. The primary components of the system are a UV light source, an intensified camera with a six-position filter wheel, and software for controlling the system and automatically analyzing the resulting images. System performance, transportability, and ruggedness were validated by using the system in a "hands-on" display at a public field day. At this event, fecal contamination of orchard apples, where dairy feces had previously been applied using stencils and then removed, was easily detected using automated edge detection and threshold detection algorithms. In addition, by applying feces to apples and then washing sets of apples at hourly intervals, it was determined that five h was the minimum contact time that allowed identification of the contamination event after the apples were washed. In addition, comparisons among images of apples contaminated with feces indicated that a 668 nm filter yielded greater contrast between fluorescence responses of apple surfaces and feces, compared to results obtained using 678 or 685 nm filters. There are many potential uses for this system, including studying the efficacy of apple washing systems.