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United States Department of Agriculture

Agricultural Research Service

Title: Optimal Fluorescence Excitation and Emission Bands for Detection of Fecal Contamination

Authors
item Kim, Moon
item Lefcourt, Alan
item Chen, Yud

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 17, 2003
Publication Date: July 1, 2003
Citation: KIM, M.S., LEFCOURT, A.M., CHEN, Y.R. OPTIMAL FLUORESCENCE EXCITATION AND EMISSION BANDS FOR DETECTION OF FECAL CONTAMINATION. JOURNAL OF FOOD PROTECTION. 66(7):1198-1207. 2003.

Interpretive Summary: Detection of fecal contamination of food products is a critical health issue. To test the feasibility of using fluorescent techniques to detect fecal contamination on agricultural commodities, fluorescence emission and excitation characteristics of fecal matter from cows, deer, swine, chickens, and turkeys in the UV to NIR regions of the spectrum were evaluated. To allow for optimization of detection of contamination on animal carcasses, emission-excitation spectra of the manures were compared to similar spectra for animal meats. Manures from dairy cows, deer, swine, turkeys, and chickens whose diet contained some green roughage showed the distinctive red-fluorescence characteristics of chlorophyll a, its metabolites, or both. Meat samples, including bones, muscle tissues, and skins, from bovines and swine and chicken showed no red fluorescence emissions. Thus, fluorescence techniques can provide the basis for the development of methodologies to detect fecal contamination on agricultural commodities including animal carcasses. The optimal excitation wavelength to allow detection of fecal contamination is about 420 nm. We suggest that detection of fecal contamination can be enhanced by incorporating green forages in the finishing diets of all farm animals. This detection methodology will be of great interest to research scientists/engineers who are developing noninvasive techniques for food safety inspection and quality grading. Food processing industry and other regulatory government agencies such as FSIS and FDA are other benefactors of this research.

Technical Abstract: To test the feasibility of using fluorescent techniques to detect fecal contamination on agricultural commodities, fluorescence emission and excitation characteristics of fecal matter from cows, deer, swine, chickens, and turkeys in the UV to NIR regions of the spectrum were evaluated. To allow for optimization of detection of contamination on animal carcasses, emission-excitation spectra of the manures were compared to similar spectra for animal meats. The feedstuffs for the swine, chickens, and turkeys were also analyzed. Blue excitation at approximately 410 to 420 nm yielded the highest fluorescence from both fecal matters and feedstuffs. Emission maxima were in the red region at 632 nm for chicken manures and 675 nm for the other species. The major constituent responsible for emission at 632 nm was tentatively identified to be protoporphyrin IX; emission at 675 nm may emanate from chlorophyll a or its metabolites such as pheophorbide a. Animal meats emitted strong fluorescence in the blue-green regions, but no emission peaks were observed in the red region. These results suggest that fluorescent emissions from naturally-occurring chlorophyll a and metabolites are good markers for fecal contamination and that, with the appropriate excitation frequency, responses of fecal matter can easily be differentiated from responses of animal carcasses. We suggest that detection of fecal contamination can be enhanced by incorporating green forages in the finishing diets of all farm animals.

Last Modified: 12/18/2014
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