Fig 1.
Optical design of line-scan RHSI system (The laser light to sample in red and scattered light from the sample in green color) (a), and photograph of a system used to acquire images from layered and mixed food powder samples (b).
Fig 2.
Software interface for image acquisition and system control.
Fig 3.
Spectral calibration for the Raman imaging system using a quadratic regression model.
Fig 4.
Schematic of sample holder for effective penetration depth determination of laser line through food powders (a), and mean Raman spectra of wheat flour of four different thickness over the adulterant material benzoyl peroxide (b).
Fig 5.
Fluorescence corrected Raman spectra of pure food powder (wheat flour (a), and paprika powder (b)) samples and adulterant materials.
Fig 6.
Raman images of 0.5% adulterated wheat flour: Images of selected wavebands for benzoyl peroxide (a) and alloxan monohydrate(b); (c) and (d) are preprocessed images of (a) and (b), respectively; (e) and (f) are binary images of (c) and (d), respectively.
Fig 7.
Preprocessed Raman images of a 1% adulterated paprika powder at selected bands of the adulterants and band summation images.
Fig 8.
Combined color coded chemical images of benzoyl peroxide (red) and alloxan monohydrate (yellow) in wheat flour (blue background) with six different concentrations and two replications.
Fig 9.
Combined color coded chemical images of Sudan dye (red) and Congo red dye (yellow) in paprika powder (blue background) with six different concentrations and two replications.
Fig 10.
Linear relationship between the pixel based calculated concentrations corrected with the ratio of densities and added mass concentration of each adulterant in wheat flour (a) and paprika powder (b).