Quantitative detection of benzoyl peroxide in wheat flour by line-scan macro-scale Raman chemical imaging

Authors: Qin, Jianwei - Tony Qin; Kim, Moon; Chao, Kuanglin - Kevin Chao; GONZALEZ, MARIA - New Mexico State University; CHO, BYOUNG-KWAN - Chungnam National University

Submitted to: Applied Spectroscopy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/2017
Publication Date: 5/9/2017
Citation: Qin, J., Kim, M.S., Chao, K., Gonzalez, M., Cho, B. 2017. Quantitative detection of benzoyl peroxide in wheat flour by line-scan macro-scale Raman chemical imaging. Applied Spectroscopy. doi:10.1177/0003702817706690.

Interpretive Summary: Quality and safety of wheat flour is an important issue worldwide since it is routinely used for making staple foods in many cultures in the world. Excessive use of benzoyl peroxide (BPO), a flour bleaching agent, in wheat flour can not only destroy the nutrients in the flour, but also cause diseases to the consumers. This study demonstrated a line-scan high-throughput Raman chemical imaging method for direct inspection of the BPO mixed in the wheat flour. Chemical images were created to detect and map the BPO particles in the flour background. The BPO can be detected at a weight by weight concentration of 50 parts per million (ppm), which is on the same level with regulatory standards. High correlation was obtained between BPO pixel concentrations in the chemical images and mass concentrations of the BPO in the flour, suggesting that the method can be used for quantitative detection of the BPO in the wheat flour. The Raman imaging inspection method can be used by regulatory agencies and food processors to authenticate the wheat flour as well as other food powders and ingredients.

Technical Abstract: A high-throughput Raman chemical imaging method was developed for direct inspection of benzoyl peroxide (BPO) mixed in wheat flour. A 5 W 785 nm line laser (240 mm long and 1 mm wide) was used as a Raman excitation source in a push-broom Raman imaging system. Hyperspectral Raman images were collected in a wavenumber range of 103–2881 cm-1 from dry wheat flour mixed with BPO at eight concentrations (w/w) from 50 to 6,400 ppm. A sample holder with a sampling volume of 150×100×2 mm3 was used to present a thin layer (2 mm thick) of the powdered sample for line-scan image acquisition. A baseline correction method based on adaptive iteratively reweighted penalized least squares was used to remove the fluctuating fluorescence signals from the wheat flour. To isolate BPO particles from the flour background, a simple thresholding method was applied to the single-band fluorescence-free images at a unique Raman peak wavenumber (i.e., 1001 cm-1) preselected for the BPO detection. Chemical images were created to detect and map the BPO particles. Limit of detection for the BPO was estimated in the order of 50 ppm, which is on the same level with regulatory standards. Pixel concentrations were calculated from the percentages of the BPO pixels in the chemical images. High correlation was found between the pixel concentrations and the mass concentrations of the BPO, indicating that the Raman chemical imaging method can be used for quantitative detection of the BPO mixed in the wheat flour.