Effects of the Adulteration Technique on the Near-Infrared Detection of Melamine in Milk Powder

Abstract

The United States Pharmacopeial Convention has led an international collaborative project to develop a toolbox of screening methods and reference standards for the detection of milk powder adulteration. During the development of adulterated milk powder reference standards, blending methods used to combine melamine and milk had unanticipated strong effects on the near-infrared (NIR) spectrum of melamine. The prominent absorbance band at 1468 nm of melamine was retained when it was dry-blended with skim milk powder but disappeared in wet-blended mixtures, where spray-dried milk powder samples were prepared from solution. Analyses using polarized light microscopy, Raman spectroscopy, dielectric relaxation spectroscopy, X-ray diffraction, and mass spectrometry indicated that wet blending promoted reversible and early Maillard reactions with lactose that are responsible for differences in melamine NIR spectra between wet- and dry-blended samples. Targeted detection estimates based solely on dry-blended reference standards are likely to overestimate NIR detection capabilities in wet-blended samples as a result of previously overlooked matrix effects arising from changes in melamine hydrogen-bonding status, covalent complexation with lactose, and the lower but more homogeneous melamine local concentration distribution produced in wet-blended samples. Techniques used to incorporate potential adulterants can determine the suitability of milk reference standards for use with rapid detection methods.

The use of NIRS in the dairy industry: New trends and applications

“…Using a variety of analytical techniques to augment NIRS, this work concluded that estimated limits of detection based solely on dry blending are likely to overestimate the detection capabilities of NIRS in wet-blended samples. 5 This is due to changes in the melamine hydrogen-bonding status, evidence for a covalent complexation with lactose and a more homogeneous melamine distribution. This work suggests that published works referring to limits of detection in the parts per million range for adulterants such as melamine in milk powder 6,7 are very optimistic.…”

Review on Nanomaterial-Based Melamine Detection

“…Recently, food safety has become a major issue due to the increase of occurrences of food poisoning [1][2][3]. For example, illegal adulteration of toxic materials, such as clenbuterol in meat and melamine in dairy product, leads to food poisoning and severe health problems [4][5][6][7][8][9][10]. In this light, melamine has been a well-known additive-with 66% nitrogen content-and is still utilized in the production of many plastics, adhesives, glues, fertilizers, plywoods, cements, cleansers, and retardant paints [11][12][13][14][15].…”

Research on a Dual-Mode Infrared Liquid-Crystal Device for Simultaneous Electrically Adjusted Filtering and Zooming

“…In recent years, the infrared detection technology [1] has been developed rapidly, because it presents several advantages including relatively long working distance, better anti-interference, full-time availability, and strong penetration of haze smoke or dust. So far, it has played a significant role in many applications such as the earth resources survey [2], global pollution and disaster warning [3,4,5], biomedical diagnosis [6,7], food safety monitoring [8,9,10,11,12], and so on. As demonstrated, the electromagnetic radiation out from targets exhibits its own specific spectral characters, which contain objective surface or structural information or chemical composition.…”