Two-dimensional hetero-spectral mid-infrared and near-infrared correlation spectroscopy for discrimination adulterated milk

• We propose a novel approach for discriminant analysis of adulterated milk.
• 2D IR/NIR correlation spectra and NPLS-DA were used to classify adulterated milk.
• The classification accuracy was 96.2% by 2D IR/NIR correlation spectra.
• The classification accuracies were 88.5% by 2D IR/IR and NIR/NIR correlation spectra.
• 2D IR/NIR correlation spectra showed better performance than 2D IR/IR and NIR/NIR.

A new approach for discriminant analysis of adulterated milk is proposed based on two-dimensional (2D) hetero-spectral near-infrared (NIR) and mid-infrared (IR) correlation spectroscopy along with multi-way partial least squares discriminant analysis (NPLS-DA). NIR transmittance spectra and IR attenuated total reflection spectra of pure milk and adulterated milk with level of melamine varying from 0.03 to 3 g·L− 1 were collected at room temperature. The synchronous 2D hetero-spectral IR/NIR correlation spectra of all samples were calculated to build a discriminant model to classify adulterated milk and pure milk. Also, the NPLS-DA models were built based on synchronous 2D homo-spectral NIR/NIR and IR/IR correlation spectra, respectively. Comparison results showed that the NPLS-DA model could provide better results using 2D hetero-spectral IR/NIR correlation spectra than using 2D homo-spectral NIR/NIR and 2D IR/IR correlation spectra.

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