Inspection of maleic anhydride in starch powder using line-scan hyperspectral Raman chemical imaging technique

Authors: Qin, Jianwei - Tony Qin; Kim, Moon; Chao, Kuanglin - Kevin Chao; BELLATO, LISA - Us Forest Service (FS); Schmidt, Walter; CHO, BYOUNGKWAN - Chungnam National University; HUANG, MIN - Jiangnan University

Submitted to: International Journal of Agricultural and Biological Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/25/2018
Publication Date: 11/1/2018
Citation: Qin, J., Kim, M.S., Chao, K., Bellato, L., Schmidt, W.F., Cho, B., Huang, M. 2018. Inspection of maleic anhydride in starch powder using line-scan hyperspectral Raman chemical imaging technique. International Journal of Agricultural and Biological Engineering. 11(6):120–125. https://doi.org/10.25165/j.ijabe.20181106.4339.
DOI: https://doi.org/10.25165/j.ijabe.20181106.4339

Interpretive Summary: As the most commonly consumer carbohydrate and a major component of many staple foods worldwide, the safety and quality of the starch is a critical issue. Maleic anhydride (MAN) is used in starch production to improve chewiness, glutinosity, and water retention of some food products, but excessive use and consumption is potentially harmful. This study developed a high-throughput Raman chemical imaging method for direct detection of MAN in the corn starch. Chemical images were generated to identify and map the MAN particles in the starch powder. The MAN can be detected at a weight-based concentration of 100 ppm (or mg/kg). Pixel concentrations of the MAN pixels in the chemical images, found to correspond to the mass concentrations of the MAN particles in the starch powder, can be used for measuring concentrations of MAN in starch. The Raman chemical imaging screening method can be used by regulatory agencies and food processors to authenticate starch powder as well as other powdered foods and ingredients.

Technical Abstract: Excessive use of maleic anhydride (MAN) in starch production is potentially harmful for consumers’ health. A macro-scale Raman chemical imaging method was developed for direct inspection and quantification of MAN particles mixed in starch powder. A 785 nm line laser was used as an excitation source in a line-scan hyperspectral Raman imaging system, which was used to acquire Raman images in a wavenumber range of 103–2831 cm-1 from corn starch mixed with MAN at eight concentrations (w/w) from 50 to 6,400 ppm. To ensure the MAN particles can be detected everywhere in the starch powder, a sample holder with a sampling volume of 150×100×2 mm3 was used to present a large surface area and thin layer of the powdered mixture for image acquisition with a spatial resolution of 0.2 mm. The fluctuating fluorescence signals from the corn starch were eliminated by a baseline correction method based on adaptive iteratively reweighted penalized least squares. Single-band fluorescence-corrected images were extracted at a unique Raman peak wavenumber (i.e., 1839 cm-1) preselected for the MAN detection, to which a simple thresholding method was used to generate chemical images for MAN detection and mapping. Limit of detection for the MAN was estimated at 100 ppm. Pixel concentrations were calculated from the percentages of the MAN pixels in the chemical images, and they were found linearly correlated with mass concentrations of the MAN particles in the starch powder. Such relationship can be used for quantitative analysis of the MAN in the starch-MAN mixtures.