Quantitative analysis of melamine in milk powders using near-infrared hyperspectral imaging and band ratio

Authors: HUANG, MIN - Jiangnan University; Kim, Moon; Delwiche, Stephen - Steve; Chao, Kuanglin - Kevin Chao; Qin, Jianwei - Tony Qin; MO, CHANGYEUN - Rural Development Administration - Korea; ESQUERRE, CARLOS - University Of Dublin; ZHU, QIBING - Jiangnan University

Submitted to: Journal of Food Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/26/2016
Publication Date: 7/1/2016
Citation: Huang, M., Kim, M.S., Delwiche, S.R., Chao, K., Qin, J., Mo, C., Esquerre, C., Zhu, Q. 2016. Quantitative analysis of melamine in milk powders using near-infrared hyperspectral imaging and band ratio. Journal of Food Engineering. 181:10-19.

Interpretive Summary: Melamine, a nitrogen rich chemical compound used in the plastics industry, is a food safety concern worldwide because of its potential nefarious use as an adulterant in milk powder and other food products to boost apparent protein content. The World Health Organization has established recommended food safety limits for this compound. Analytical laboratories traditionally rely on highly technical methods for detecting melamine contamination levels, however these methods require levels of operator skill and analysis time that make them ill-suited for industrial food processing facilities. Near infrared hyperspectral imaging is a simpler technique that utilizes light wavelengths just beyond the visible light region to analyze food products. This technique offers a potential alternative for melamine adulterant detection. Using whole milk and nonfat milk powders, mixtures of these substances contaminated with melamine were prepared in the laboratory and scanned using hyperspectral imaging. Using this technology, we were able to accurately estimate the level of melamine contaminant in milk products. This work has the potential to benefit manufacturers of milk powder, and possibly other food powder manufacturers, by offering a method that is adaptable to industrial food processing facilities.

Technical Abstract: Since 2008, the detection of the adulterant melamine (2,4,6-triamino-1,3,5-triazine) in food products has become the subject of research due to several food safety scares. Near-infrared (NIR) hyperspectral imaging offers great potential for food safety and quality research because it combines the features of vibrational spectroscopy and digital imaging. In this study, NIR hyperspectral imaging was investigated for quantitative evaluation of melamine particles in nonfat and whole milk powders. Melamine was mixed into milk powders in a concentration range of 0.02 -1.00% (w/w). A NIR hyperspectral imaging system was used to acquire images (938 -1654 nm) of melamine powder, whole milk powder, nonfat milk powder, and mixtures of melamine and each of the milk powders. Two optimal bands (1447 nm and 1466 nm) were selected by a linear correlation algorithm with pure milk and pure melamine. Band ratio (B1447/1466) images coupled with a single threshold were used to create resultant images to visualize identification and distribution of the melamine adulterant particles in milk powders. The identification results were verified by spectral feature comparison between separated mean spectra of melamine pixels and milk pixels. Linear correlations (r) were found between the number of pixels identified as containing melamine and melamine concentration in nonfat milk and whole milk powders, which were 0.980 and 0.970 or higher, respectively. The study demonstrated that the combination of NIR hyperspectral imaging and simple band ratioing was promising for rapid quantitative analysis of melamine in milk powders.