Application of Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy coupled with chemometrics for detection and quantification of formalin in cow milk

Abstract

Milk is the best and cheapest source of nutrition and hence adulteration in milk is done to gain economic benefit. Formalin has been added illegitimately in order to increase the shelf life of milk. Fourier transform infrared (FTIR) spectroscopy coupled with multivariate chemometrics was evaluated as a quick quality monitoring method for the qualitative and quantitative analysis of formalin in cow milk. Spectra of pure and adulterated milk (0.5–5 % v/v) were acquired in the wavenumber range of 4000−400 cm−1 using ATR-FTIR. Principal component analysis (PCA) showed well separated clusters allowing discrimination of pure samples from adulterated samples. Soft Independent Modelling of Class Analogy (SIMCA) approach was applied for the classification of test samples which showed 100 % classification efficiency. Partial least squares (PLS) regression and Principle component regression (PCR) models were established to quantify the level of formalin in milk using normal, 1st derivative and 2nd derivative spectra. PLSR model for normal spectra showed best prediction as compared to PCR with coefficient of determination (R2) of 0.977 for calibration and 0.985 for validation. This method has a sensitivity of 0.5 % level of formalin adulteration.