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Submitted to: Proceedings of SPIE
Publication Type: Proceedings Publication Acceptance Date: 5/18/2015 Publication Date: 5/20/2015 Citation: Qin, J., Chao, K., Kim, M.S. 2015. Screening of adulterants in powdered foods and ingredients using line-scan Raman chemical imaging. Proceedings of SPIE 9488, Sensing for Agriculture and Food Quality and Safety VII, 94880F. Interpretive Summary: Economically motivated adulteration of food ingredients can cause illness and death for consumers, as illustrated by various incidents involving melamine contamination of milk and wheat gluten. The result has been increased interest in developing rapid and accurate screening method for authenticating food materials for both safety and quality issues. Our previous studies have demonstrated that Raman chemical imaging technique can be used to detect various adulterants in milk powder. One limitation of our previous approach was the long sampling time (typically in hours) needed for the point-scan Raman imaging system to collect the sample images, which prevents it from performing fast inspection for the milk powder. A line-scan high-throughput Raman imaging system was used in this study to investigate Raman imaging and analysis technique better suited to screening food samples for inspection purposes. Samples on a motorized table are imaged by a line-scan Raman technique utilizing a laser line projected across the sample surface. Images were acquired for 0.5% sample mixtures of melamine in milk powder, benzoyl peroxide in flour, and maleic anhydride in starch, with each sample evenly spread across a 50 mm×50 mm square area for imaging. Spectral and image processing algorithms were developed for each chemical adulterant based on its Raman spectral characteristics. Chemical images were created to show identification, spatial distribution, and morphological features of the adulterant particles mixed in the food powders. The methods developed in this study has great potential for use in quantitative detection and concentration estimation of adulterants in dry food ingredients by the food industry and regulatory agencies. Technical Abstract: A newly developed line-scan Raman imaging system using a 785 nm line laser was used to authenticate powdered foods and ingredients. The system was used to collect hyperspectral Raman images in the range of 102–2865 wavenumber from three representative food powders mixed with selected adulterants each at a concentration of 0.5%, including milk and melamine, flour and benzoyl peroxide, and starch and maleic anhydride. An acoustic mixer was used to ensure uniform mixing of the food adulterant mixtures. All the mixed samples were spread across sample holders with a surface area of 50 mm×50 mm for sample imaging. Spectral and image processing algorithms were developed based on single-band images at the unique Raman peaks of the individual adulterants. Chemical images were created to show identification, spatial distribution, and morphological features of the adulterant particles mixed in the food powders. The potential of estimating mass concentrations of the adulterants using the percentages of the adulterant pixels in the chemical images was also demonstrated. |
