Non-targeted detection of milk powder adulteration using Raman spectroscopy and chemometrics: melamine case study

ABSTRACT

Raman spectroscopy in combination with chemometrics was explored as a rapid, non-targeted screening method for the detection of milk powder (MP) adulteration using melamine as an example contaminant. Raman spectroscopy and an unsupervised pattern-recognition method, principal component analysis (PCA), allowed for the differentiation of authentic MPs from adulterated ones at concentrations > 1.0% for dry-blended (DB) samples and > 0.30% for wet-blended (WB) ones. Soft independent modelling of class analogy (SIMCA), a supervised pattern-recognition method, was also used to classify test samples as adulterated or authentic. Combined statistics at a 97% confidence level from the SIMCA models correctly classified adulteration of MP with melamine at concentrations ≥ 0.5% for DB samples and ≥ 0.30% for WB ones, while no false-positives from authentic MPs were found when the spectra in the 600–700 cm^–1 range were pre-processed using standard normal variate (SNV) followed by a gap-segment derivatisation. The combined technique of Raman spectroscopy and chemometrics proved to be a useful tool for the rapid and cost-efficient non-targeted detection of adulteration in MP at per cent spiking levels.

GRAPHICAL ABSTRACT

KEYWORDS:

• Skim milk powder (SMP)
• non-fat dry milk powder (NFDM)
• economic adulteration
• Raman spectroscopy
• PCA
• soft independent modelling of class analogy (SIMCA)
• non-targeted detection
• classification

Acknowledgments

The authors thank Steven Zbylut, Andrew Mackey, Jianwei Qin, Moon Kim, Kevin Chao, Lucy Botros and Robert Magaletta for discussions on Raman spectroscopy and milk powder evaluation.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

The supplemental material for this article can be accessed here.

Additional information

Funding

S. R. K. acknowledges the support provided by an appointment to the Research Participation Program at the Center for Food Safety and Applied Nutrition, administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the US Department of Energy and the US Food and Drug Administration (USFDA).