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United States Department of Agriculture

Agricultural Research Service

Title: Ns-Scale Time-Resolved Laser Induced Fluorescence Imaging for Detection of Fecal Contamination on Apples

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

Submitted to: Proceedings of SPIE
Publication Type: Proceedings
Publication Acceptance Date: October 26, 2004
Publication Date: October 27, 2005
Citation: Kim, M.S., Lefcourt, A.M., Chen, Y.R.. 2004. NS-scale time-resolved laser induced flourescence imaging for detection of fecal contamination on apples. In: Chen, Y.R., Tu, Shu-I., editors. Nondestructive Sensing for Food Safety, Quality, and Natual Resources. The International Society for Optical Engineering Conference, October 27-28, 2004, Philadelphia, Pennsylvania. p. 190-197.

Interpretive Summary: Our laboratory has been exploring fluorescence as a potential means for detection of fecal contamination on post-harvest fruits. Researchers at the ISL have developed a new laser induced fluorescence imaging system based on nanosecond scale time-resolved fluorescence techniques. Time-dependent multispectral fluorescence emissions of apples contaminated with a range of diluted cow feces were acquired. Four spectral bands, F670, F680, F685 and F730, centered near the red fluorescence emission peak wavelengths from apples artificially contaminated with cow feces were examined to determine optimal red fluorescence band and ns-gate window for detection of fecal contamination on apples. The results showed that 10 nm wide 670 nm band with a gate-delay of 4 ns from the laser excitation peak provided the greatest differences in time-dependent fluorescence responses between feces contaminated spots and apples surfaces. Presented sensing systems and methodologies are useful to food scientists, engineers, regulatory government agencies (FSIS and FDA), and food processing industries.

Technical Abstract: Our laboratory has been utilizing fluorescence techniques as a potential means for detection of quality and wholesomeness of food products. A system with a short pulse light source such as a laser coupled with a gated detector can be used to harvest fluorescence in ambient light conditions from biological samples with relatively low fluorescence yields. We present a versatile multispectral laser-induced fluorescence (LIF) imaging system capable of ns-scale time resolved fluorescence. The system is equipped with a tunable pulse laser system that emits in the visible range from 410 nm to 690 nm. Ns-scale, time-dependent multispectral fluorescence emissions of apples contaminated with a range of diluted cow feces were acquired. Four spectral bands, F670, F680, F685 and F730, centered near the emission peak wavelengths of the major constituents responsible for the red fluorescence emissions from apples artificially contaminated with cow feces were examined to determine a suitable single red fluorescence band and optimal ns-gate window for detection of fecal contamination on apples. The results based on the ns decay curves showed that 670 nm with 10 nm full width at half maximum (FWHM) at a gate-delay of 4 ns from the laser excitation peak provided the greatest differences in time-dependent fluorescence responses between feces contaminated spots and apples surfaces.

Last Modified: 9/10/2014
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