Comparative Evaluation of Cow and Goat Milk Samples Utilizing Non-Destructive Techniques and Chemometric Approaches

This study applied a multi-analytical methodology involving Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy, protein secondary structure determination, colorimetry, and texture analysis of milk images at a microscopic level to characterize 47 commercial cow and goat milk samples of different fat content (whole and light). Colorimetric measurements showed that hue values were significantly higher in light than in whole milks, providing a rapid marker of fat level, while microscopic image analysis indicated that whole milks had more heterogeneous textures with larger fat globules, whereas light milks were more homogeneous. ATR-FTIR spectra revealed lipids, proteins, and carbohydrates as the main constituents; lipid-associated bands were more intense in whole milks, whereas carbohydrate-associated bands, particularly at 1026–1028 cm−1, were stronger in cow milk. Protein secondary structure analysis confirmed β-parallel sheet as the predominant motif, with cow milk showing higher random coil and α-helix proportions and goat milk enriched in β-turn structures. Chemometric modeling using PCA and PLS-DA achieved robust classification of samples by species and fat content, while Receiver Operation Characteristics (ROC) analysis validated markers of differentiation. The combination of the above methodologies enables effective classification of cow’s and goat’s milk, offering a thorough product description.