Investigation of the presence of rod-shaped bacteria on food surface via elastic light scattering

We investigated the presence and related signal-tonoise ratio (SNR) of rod-shaped bacteria on a produce surface using elastic scattering. The theoretical noise was defined as a scattering signal from a rough produce surface while the signal was defined as a scattering signal from the increasing numbers of rod-shaped bacteria on the produce surface. In this research, we measured the surface topography of a tomato using BioAFM to provide the quantitative nature of the surface roughness which was, in turn, modeled with the discrete dipole approximation (DDA) for an accurate estimation of the background scattering signature. Then we included the DDA model of rod-shaped bacteria and calculated the combined elastic scattering signature in the upper hemispherical space with different polarizations, wavelengths, and incident angles. The total scattering cross-section (TSC) and partial scattering cross-section (PSC) were both computed on six predefined aperture locations. The results indicate that, upon proper selection of the wavelength and incident angle, it was possible to provide the minimum number of bacteria (~32) to provide a differentiable elastic scattering signal from the produce surface.