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United States Department of Agriculture

Agricultural Research Service


item Ashby, Kyle - IOWA STATE UNIV., AMES
item Casey, Thomas
item Petrich, Jacob - IOWA STATE UNIV., AMES
item Rasmussen, Mark

Submitted to: Association Official Analytical Chemists Annual Intrl Meeting & Exposition
Publication Type: Abstract Only
Publication Acceptance Date: September 27, 1999
Publication Date: N/A

Technical Abstract: Public concern over E. coli O157:H7 has risen dramatically over the past several years. Ingestion of undercooked meat containing these bacteria leads to serious illness and possible death. E. coli O157:H7 is found in the feces of livestock and is spread to the meat carcass by fecal contamination during processing. While many methods detect or count the actual bacteria to determine if meat is contaminated, often taking several hours, we describe a method based upon fluorescence spectroscopy to detect the feces, the substrate for the bacteria, which provides an instantaneous determination of meat contamination. This "instantaneous" signal, which has a time constant on the order of 100 ms, allows for the detection to occur on the production line of the meat production facility. Chlorophyll "a" metabolites in the feces are detected by fluorescence in the red part of the visible spectrum (670 nm) when excited by green laser light which is smodulated and coupled through a fiber optic. The fluorescence is coupled through the same fiber or a different fiber onto photomultiplier tube detectors. The system uses phase sensitive detection by utilizing lock-in amplifiers. All components of the system have been built into a detector no larger than 31x31x16 cm and can be easily handled and carried. Pheophorbide "a", one of the major chlorphyll "a" metabolites, can be detected to a limit on the order of 10**-9 M in solution.

Last Modified: 7/29/2016