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Proceedings Paper

Discrimination of bacteria on food using laser-induced bacterial autofluorescence
Author(s): Peter J. Hilton; Manfred Plagmann
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Paper Abstract

This paper updates progress on work1 in detecting bacterial auto-fluorescence against various food backgrounds using Laser-Induced Fluorescence (LIE). The fluorescence of bacteria and various meat products has been measured in order to find suitable excitation and detection wavelengths for discriminative imaging. The optical absorption of bacteria, meat and fish tissue was measured to provide a starting point for the fluorescence measurements. The bacteria measured was Escherichia Coli, and the food tissue products were, lamb, pork, chicken and fish. All absorption spectra have a peak around 400nm and most muscle tissue types have lower absorption around 325nm giving a good low contrast fluorescent background for the F. Coli. However, other tissue types such as fat, skin and bone skin have higher absorption levels and hence fluorescence. Three interference filters can be used to selectively sample the fluorescence spectra to generate a three point intensity ratio that can be used to discriminate between fluorescence of the various tissue types and E. Coli. The best fluorescence discrimination was achieved using the HeCd laser wavelength of 325nm. However in our current experimental setup there is not enough optical power at 325nm for direct laser imaging. We are currently working to increase UV laser excitation levels by using a dye laser to pump a frequency doubling crystal.

Paper Details

Date Published: 15 December 2000
PDF: 7 pages
Proc. SPIE 4087, Applications of Photonic Technology 4, (15 December 2000); doi: 10.1117/12.406343
Show Author Affiliations
Peter J. Hilton, Industrial Research Ltd. (New Zealand)
Manfred Plagmann, Industrial Research Ltd. (New Zealand)

Published in SPIE Proceedings Vol. 4087:
Applications of Photonic Technology 4
Roger A. Lessard; George A. Lampropoulos, Editor(s)

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