Hyperspectral fluorescence imaging using violet LEDs as excitation sources for fecal matter contaminate identification on spinach leaves

摘要

Food safety in the production of fresh produce for human consumption is a worldwide issue and needs to be addressed to decrease foodborne illnesses and resulting costs. Hyperspectral fluorescence imaging coupled with multivariate image analysis techniques for detection of fecal contaminates on spinach leaves (Spinacia oleracea) was evaluated. Violet fluorescence excitation was provided at 405 nm and light emission was recorded from 464 to 800 nm. Partial least square discriminant analysis and wavelength ratio methods were compared for detection accuracy for fecal contamination. Fluorescence emission profiles of spinach leaves were monitored over a 27 days storage period; peak emission blue-shifts were observed over the storage period accompanying acolor change from green to green–yellow–brown hue. The PLSDA model developed correctly detected fecal contamination on 100 % of relatively fresh green spinach leaves used in this investigation, which also had soil contamination. The PLSDA model had 19% false positives for non-fresh post storage leaves. A wavelength ratio technique using four wavebands (680, 688, 703 and 723 nm) was successful in identifying 100 % of fecal contaminates on both fresh and non-fresh leaves. An on-line fluorescence imaging inspection system for fecal contaminant detection has potential to allow fresh produce producers to reduce foodborne illnesses and prevent against the associated economic losses.