Surface and subsurface inspection of food safety and quality using a line-scan Raman system

Authors: Qin, Jianwei - Tony Qin; Kim, Moon; Chao, Kuanglin - Kevin Chao; Schmidt, Walter; Delwiche, Stephen - Steve

Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: 6/20/2016
Publication Date: 7/18/2016
Citation: Qin, J., Kim, M.S., Chao, K., Schmidt, W.F., Delwiche, S.R. 2016. Surface and subsurface inspection of food safety and quality using a line-scan Raman system. ASABE Annual International Meeting, St. Joseph, MI. ASABE Paper No. 162460315.

Interpretive Summary: Food safety and quality attributes (e.g., fruit surface contamination and flesh quality under skin) can be at different sample locations. Thus both surface and subsurface inspection of food and agricultural products is important. This paper presents a line-scan Raman imaging and spectroscopy platform for food safety and quality research. The platform can be configured for two modes: line-laser Raman chemical imaging (RCI) mode for food surface evaluation and point-laser spatially offset Raman spectroscopy (SORS) mode for food subsurface evaluation. Example applications for a pork shoulder, an orange carrot, and a carrot-on-melamine layered sample demonstrated the capabilities of this new tool for surface and subsurface inspection for food safety and quality. The method and the system will be useful to regulatory agencies (e.g., FDA and USDA FSIS) with an interest in enforcing standards of food safety and quality, and also to food processors and inspectors in ensuring the safety and quality of the food products.

Technical Abstract: This paper presents a line-scan Raman platform for food safety and quality research, which can be configured for Raman chemical imaging (RCI) mode for surface inspection and spatially offset Raman spectroscopy (SORS) mode for subsurface inspection. In the RCI mode, macro-scale imaging was achieved using a 785 nm line laser up to 24 cm long with a push-broom method. In the SORS mode, a 785 nm point laser was used and a complete set of SORS data was collected in an offset range of 0–36 mm with a spatial interval of 0.07 mm using one CCD exposure. The RCI and SORS modes share a common detection module including an imaging spectrograph and a CCD camera, covering a Raman shift range from -674 to 2865 cm-1. A pork shoulder and an orange carrot were used to test large-field-of-view (230 mm wide) and high-spatial-resolution (0.07 mm/pixel) settings of the RCI mode for food surface evaluation. Fluorescence-corrected images at selected Raman peaks were used to view Raman-active analytes on the whole sample surfaces (e.g., fat on the pork shoulder and carotenoids over the carrot cross section).Also, a layered sample, which was created by placing a 5 mm thick carrot slice on top of melamine powder, was used to test the SORS mode for subsurface food evaluation. Raman spectra from carrot and melamine were successfully resolved using self-modeling mixture analysis. The line-scan Raman imaging and spectroscopy platform provides a new tool for surface and subsurface inspection for food safety and quality.