Optical Parameters for Using Visible-Wavelength Reflectance or Fluorescence Imaging to Detect Bird Excrements in Produce Fields

Alan Lefcourt,Paula Rivadeneira,Mark Siemens

doi:10.3390/app9040715

Alan Lefcourt, Paula Rivadeneira + Show 1 more

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Consumption of produce contaminated with pathogens of fecal origin is the most common source of food borne illnesses. Current practice is to visually survey fields for evidence of fecal contamination, and to exclude problematic areas from harvest. Bird excrement is known to contain human pathogens, and is often not detectable in produce fields using current survey methods. The goal of this project was to identify parameters for optical detection of bird excrements to support development of instruments to be used to supplement existing visual surveys. Under daylight ambient conditions, results suggested that reflectance imaging at around 500–530 nm or 610–640 nm could be used to detect excrements from the three bird species tested. Images were acquired using ad hoc camera parameters; however, normalizing intensities for individual images at 525 nm and using a fixed detection threshold allowed detection of 100% of bird excrements with no false positives against the background that consisted of local soil and fresh romaine and spinach leaves. Similar results were obtained using fluorescence imaging. Fluorescent imaging was accomplished in a darkened room using 405-nm illumination. The largest consistent differences in intensity responses between excrements and the brightest non-excrement object in the background matrix occurred at around 550 nm. Results suggested that using reflectance or fluorescence imaging for detection of bird excrements could be a valuable tool for reducing risks of consuming contaminated produce. One possibility would be to incorporate appropriate reflectance imaging capabilities in drones under the control of the individuals currently conducting field surveys.

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Produce contaminated with fecal-derived pathogens is a recognized food-safety concern
We recently demonstrated that dairy manure could be reliably detected using fluorescence imaging at dusk or at night [17]
Prior work had demonstrated that using reflectance spectral imaging to detect fecal materials from animals such as cows was possible with a high rate of detection confounded by some specific classes of false positives [18], and that fluorescence spectral imaging could achieve

Summary

Introduction

Produce contaminated with fecal-derived pathogens is a recognized food-safety concern. Current practice is to visually survey fields prior to harvest for signs of fecal contamination, and to restrict harvesting of identified problem areas. The difficulty of detecting bird droppings in fields is a concern. To address this concern, this study examined optical parameters and methods that could be used to develop optical survey instruments to detect bird droppings in produce fields. Fresh produce represents a particular food-safety risk as it is commonly consumed fresh, without an intervening kill step such as cooking to reduce any potential pathogen load. Painter et al [1] reported that produce is the most common source of food borne illnesses, and incidences of produce-related food-safety events have been increasing in recent years [2].

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