Detection of Urea Adulteration in Milk Using Near-Infrared Raman Spectroscopy

We report results of a spectroscopic study to assess the applicability of near-infrared Raman spectroscopy for quantitative determination of urea adulteration in milk without any preprocessing requirement. Different batches of milk adulteration were prepared with each batch containing milk samples added with urea at various concentrations ranging from 10 to 1,000 mg/dl. The Raman spectra were measured from these urea-mixed milk samples with a Raman spectroscopy setup that incorporates a 785-nm diode laser for Raman excitation. An algorithm based on partial least square (PLS) regression was developed to quantitatively predict the concentration of urea based on the measured sets of Raman spectra of the urea-mixed milk samples. The results showed that Raman spectroscopy in combination with the PLS-based chemometric algorithm could detect urea mixed in milk samples with an accuracy of > 90 %.