Detection of fecal contamination on apples with nanosecond-scale time-resolved imaging of laser-induced fluorescence

Detection of apples contaminated with feces is a public health concern. We found that time-resolved imaging of apples artificially contaminated with feces allowed optimization of timing parameters for detection. Dairy feces were applied to Red Delicious and Golden Delicious apples. Laser-induced fluorescence responses were imaged by use of a gated intensified camera. We developed algorithms to automatically detect contamination iteratively by using one half of the apples and validated them by applying the optimized algorithms to the remaining apples. Results show that consideration of the timing of fluorescence responses to pulsed-laser excitation can enhance detection of feces on apples.