A 1064 nm dispersive Raman spectral imaging system for food safety and quality evaluation

Authors: Chao, Kuanglin - Kevin Chao; DHAKAL, SAGAR - Forest Service (FS); Qin, Jianwei - Tony Qin; Kim, Moon; PENG, YANKUN - China Agricultural University

Submitted to: Applied Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/9/2018
Publication Date: 3/13/2018
Citation: Chao, K., Dhakal, S., Qin, J., Kim, M.S., Peng, Y. 2018. A 1064 nm dispersive Raman spectral imaging system for food safety and quality evaluation. Applied Sciences. 8(3):431.

Interpretive Summary: A 1064 nm Raman spectral imaging system was developed for food safety and quality research. The application of the Raman spectral system was demonstrated by detecting metanil yellow contamination in turmeric powder at five concentration levels. A hyperspectral Raman image of the mixture sample at each concentration was collected covering the sample surface area of 25 mm x 25 mm. The system could detect metanil yellow at concentrations as low as 1%. Application of the system for subsurface measurement was demonstrated by detection of gelatin-encapsulated pure and mixed samples of turmeric and metanil yellow powder. The system is a versatile platform capable of acquiring Raman spectral image for a wide variety of food and pharmaceutical samples, and it is useful for safety and quality evaluation of food and agricultural products.

Technical Abstract: Raman spectral imaging is an effective method to analyze and evaluate chemical composition and structure of a sample, and has many applications for food safety and quality research. This study developed a 1064 nm Raman spectral imaging system for surface and subsurface analysis of food samples. A 1064 nm laser module is used for sample excitation. A bifurcated optical fiber coupled with Raman probe is used to focus excitation laser on the sample and carry scattering signal to the spectrograph. A high throughput volume phase grating disperses the incoming Raman signal. A 512 pixels InGaAs detector receives the dispersed light signal. A motorized positioning table moves the sample in two-axis directions, accumulating hyperspectral image of the sample by the point-scan method. An interface software was developed in-house for parameterization, data acquisition, and data transfer. The system was spectrally calibrated using naphthalene and polystyrene. It has the Raman shift range of 142 cm-1 to 1820 cm-1, the spectral resolution of 12 cm-1 at FWHM and the spatial resolution of 0.1 mm. Application of the system was demonstrated by surface and subsurface detection of metanil yellow contamination in turmeric powder. Results indicate that the 1064 nm Raman system is a useful tool for food safety and quality evaluation.