Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 20, 2002
Publication Date: August 20, 2002
Citation: Kim, M.S., Lefcourt, A.M., Chen, Y.R., Kim, I., Chan, D.E., Chao, K. 2002. Multispectral detection of fecal contamination on apples based on hyperspectral imagery - part ii: application of hyperspectral fluorescence imaging. Transactions of the ASAE. 46(2):2039-2047. Interpretive Summary: A number of natural compounds emit fluorescence in the visible region when illuminated with light in the ultraviolet region of the spectrum. This investigation illustrated a systematic approach using hyperspectral fluorescence imaging technique in conjunction with image processing algorithms to define several optimal wavelengths to detect fecal contaminated spots on apples. We identified four multispectral bands (450 530, 685, and 735 nm) as being the optimal bands to allow discrimination of contaminated apple surfaces. Furthermore, the simple two-band fluorescence ratios (e.g., 685 to 450 nm) reduced the variations in normal apple surfaces while accentuating differences between fecal contaminated and uncontaminated areas. This was demonstrated in the presence of large variations of normal apples due to inherent morphological and skin coloration factors. We demonstrated the high sensitivity of the fluorescence imaging techniques where the feces contaminated surfaces not readily visible to human eye were detected. The optimal fluorescence bands and the ratio algorithms can be implemented to on-line fluorescence imaging systems for detection of fecal contamination. This research is useful to government and industry scientists/engineers who are developing noninvasive sensor systems for detection of contaminations on food commodities. Furthermore, multispectral bands and imaging techniques can be implemented in food processing plants to provide a rapid means of detecting fecal contamination on agricultural products.
Technical Abstract: Pathogenic E. coli contamination in unpasteurized apple juice or cider is thought to originate from animal feces, and fecal contamination of apples has been recognized by the FDA as an important health issue. In a companion paper, reflectance imaging techniques were shown ineffective for the detection of thin smears of feces applied to apples. The objective of this study was to evaluate the use of fluorescence imaging techniques to detect fecal contamination on apple surfaces. A hyperspectral imaging system based on a spectrograph, camera, and UV light source was used to obtain hyperspectral images of Red Delicious, Fuji, Golden Delicious and Gala apples. Fresh dairy feces were applied to each apple as both a thick patch and as a thin smear. Results indicate that multispectral fluorescence techniques can be used to effectively detect fecal contamination on apple surfaces. Both principal component analysis and examination of emission maxima identified the same four multispectral bands (450, 530, 685, and 73 nm) as being the optimal bands to allow discrimination of contaminated apple surfaces. Furthermore, the simple two-band ratio (e.g., 685 to 450 nm) reduced the variation in normal apple surfaces while accentuating differences between contaminated and uncontaminated areas. Because of the limited sample size, delineation of an optimal detection scheme is beyond the scope of the current study. However, the results suggest that use of multispectral fluorescence techniques for detection of fecal contamination on apples in a commercial setting may be feasible.