Hyperspectral Determination of Fluorescence Wavebands for Multispectral Imaging Detection of Multiple Animal Fecal Species Contaminations on Romaine Lettuce

Abstract

Consumption of fresh produce has been linked to multiple outbreaks of serious foodborne illnesses over the past two decades, and the popularity growth of ready-to-eat fruit and vegetable products may be related to the increased incidence of produce-related outbreaks. Because the sources of the pathogenic microorganisms most frequently involved in these outbreaks, E. coli O157: H7 and Salmonella, have been attributed primarily to animal fecal matter, research examining routes of fecal contamination and developing methods to prevent them have been areas of recent emphasis. This investigation used non-destructive hyperspectral fluorescence imaging to evaluate relatively simple spectral classification algorithms—using single wavebands or two-band ratios—for detecting animal feces contamination on leafy greens. In particular, this study sought to detect and discriminate between feces contamination from four animal species on romaine lettuce leaves. Single fluorescence wavebands found to be effective for discriminating feces from dairy cattle, pig, chicken, and sheep were F641 nm, F505 nm, F633 nm, and F645 nm, respectively. A two-band ratio in the range of F664 ± 4 nm/F694 ± 2 nm was shown to have a detection accuracy of over 93% for undiluted feces and 1:20 and 1:50 fecal dilutions for three of the four fecal species. The spectral bands identified in this hyperspectral imaging study can be implemented for use in a relatively simple portable hand-held imaging device for on-site safety evaluation of produce in the field.