Detection and Quantification of Urea in Milk Using Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy

Milk adulteration with synthetic chemicals is a serious concern for human health. Urea is added in milk which causes severe stomach ailments. Potential of attenuated total reflectance (ATR)-Fourier transform infrared (FTIR) spectroscopy was evaluated for rapid detection and quantification of added urea in milk. Altogether, 210 spectra (4000-700 cm(-1)) of milk adulterated with known urea concentration (viz., 100 ppm, 500 ppm, 700 ppm, 900 ppm, 1300 ppm, and 2000 ppm) were analyzed. The spectral range of 1670-1564 cm(-1) comprising four smaller spectral regions (1670-1653, 1649-1621, 1615-1580, and 1594-1564 cm(-1)) showed clear differences in absorption values. Pattern recognition analysis using Soft Independent Modeling of Class Analogy (SIMCA) provided well-separated clusters, viz., pure milk and urea < 900 ppm and urea > 900 ppm. Quantity of urea was best predicted in the spectral range of 1649-1621 and 1611-1580 cm(-1) using partial least square (PLS) regression with coefficient of determination 0.906 and 0.879 for calibration and validation, respectively.