New Spectroscopic Method Detects Milk Powder Adulteration at Sub-PPM Levels

A team of researchers at the International University for Science and Technology (IUST) in Syria recently developed a reagent-free analytical technique capable of detecting the industrial chemical melamine in milk powder at concentrations as low as 0.46 parts per million. Their study, published in the journal Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, demonstrates how their method can improve on the sensitivity of conventional infrared (IR) spectroscopy methods currently used in food quality control.¹

Have spectroscopic methods been used to analyze milk powder adulteration before?

There have been several studies that have explored using molecular and vibrational spectroscopic techniques to detect adulteration in food products, including milk powder. For example, researchers at Shanghai University developed a new method using Raman spectroscopy and chemometric modeling to identify and quantify animal-origin milk powders and detect adulteration.² In this particular study, the team applied a MultiClass Classifier for qualitative analysis and partial least squares regression (PLSR) plus support vector machine regression (SVR) for quantification.² Results showed over 93% classification accuracy, with strong linear correlations (R² > 0.95) and minimal errors.²

Meanwhile, another study demonstrated that a portable near-infrared (NIR) spectrometer can rapidly and accurately detect wheat flour adulteration in milk powder through both qualitative and quantitative analysis.³ Using chemometric techniques such as principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA), support vector classification (SVC), partial least squares regression (PLSR), and support vector machine regression (SVR), researchers achieved 100% accuracy in classifying adulterated samples and precisely quantified contamination levels.³

Why is studying and detecting adulteration in milk powder important?

Studying milk powder adulteration is important because it is among the most frequently adulterated food commodities in global trade. Melamine, a nitrogen-rich industrial compound, has been fraudulently added to dairy products to artificially inflate apparent protein content during standard nitrogen-based testing, which is a practice linked to serious public health incidents, most notably a 2008 contamination crisis in China that sickened hundreds of thousands of infants.¹

What did the researchers at International University for Science and Technology (IUST) do in their study?

In their study, the research team combined Fourier transform infrared spectroscopy (FT-IR) with two-trace two-dimensional correlation spectroscopy (2T2D-COS) to identify trace adulterants in powdered milk samples.¹

So how did this new method work? As the researchers described in their article, their method works by analyzing cross-peak correlation intensities in the IR spectra of two samples simultaneously.¹ The research team found that asynchronous correlation intensities at specific wavenumbers (814 and 1,741 cm⁻¹) increased linearly with the difference in melamine concentration between the two analyzed spectra, enabling the construction of a quantitative calibration curve.¹ That linearity is what allows the technique to function not merely as a detection tool but as a measurement method.¹

What benefits do two-trace 2D correlation spectroscopy (2T2D-COS)?

The key benefit of this technique is its sensitivity. Standard second-derivative FT-IR analysis, a commonly used method for this application, performs less reliably at trace concentrations.¹ The 2T2D-COS approach effectively enhances spectral resolution without introducing new reagents or sample preparation steps, keeping the workflow practical for routine laboratory use.¹

According to the researchers, what makes this study different is that because 2T2D-COS can be applied quantitatively, it is a departure from its prior use as a purely qualitative or interpretive tool.¹

For food testing laboratories and regulatory bodies, the findings offer a pathway to more reliable, low-cost screening of powdered dairy products at the trace levels most relevant to deliberate adulteration.

References

1. Al Lafi, A. G.; Al Naser, I.; Abboud, H. Two-trace Two-Dimensional Correlation Spectroscopy (2T2D-COS) Approach to Analyze Fourier transform Infrared (FT-IR) Spectroscopic Data of Melamine Adulterated Milk Powder: A Quantitative Approach. Spectrochimica Acta Part A: Mol. Biomol. Spectrosc. 2026, 360, 128008. DOI: 10.1016/j.saa.2026.128008
2. Wetzel, W. Advancing Milk Powder Authentication with Raman Spectroscopy and Chemometrics. Spectroscopy. Available at: https://www.spectroscopyonline.com/view/advancing-milk-powder-authentication-with-raman-spectroscopy-and-chemometrics (accessed 2026-05-14).
3. Mei, C.; Deng, J.; Jiang, H. Rapid Qualitative and Quantitative Identification of Adulterated Wheat Flour in Edible Milk Powder by a Portable Near-infrared Spectroscopy. Spectrochimica Acta Part A: Mol. Biomol. Spectrosc. 2026, 355, 127693. DOI: 10.1016/j.saa.2026.127693