Thirty samples of each concentration (altogether 210 samples)
were drawn and kept in test tubes at 30 °C. The absorption
spectra of these samples were acquired using Fourier transformed
infrared (FTIR) spectrometer with Diamond crystal
cell ATR (path length: 1.66 μm; Bruker, Model-Alpha, Germany)
at 4 cm−1 resolution, 0.2 cm s−1 scan speed, and 24
scans of each sample at 30 °C in the wavenumber range of
4000–700 cm−1 . As the milk is oil in water emulsion, the
reference (background) spectra of double-distilled water using
ATR crystal were recorded at an interval of 30 samples. The
reference spectra were used by the instrument in rationing the
spectra of the samples in the absorbance unit. After scanning
each sample, the ATR crystal was wiped dry using a soft tissue
paper and spectrometrically examined for the presence of any
remnants. The cleanliness of ATR crystal was verified by
collecting a background spectrum and comparing it to the
previous one. Altogether, 210 spectra of controlled (pure
milk) and adulterated samples were acquired.