In-situ authentication of goat milk in terms of its adulteration with cow milk using a low-cost portable NIR spectrophotometer

Abstract

This work aimed at the use of a miniaturized near-infrared (NIR) spectrophotometer for the in-situ goat milk authentication in terms of its adulteration by adding cow milk. For this, One-Class Partial Least Squares (OC-PLS), PLS for Discriminant Analysis (PLS-DA), and the Successive Projections Algorithm for interval selection in PLS-DA (iSPA-PLS-DA) were employed. OC-PLS misclassified 1 pure goat milk sample as adulterated and 49 adulterated sample as pure in the test set, while PLS-DA misclassified 1 adulterated sample as pure goat milk and 2 pure goat milk samples as adulterated in the test set. On the other hand, the best predictive ability was achieved by iSPA-PLS-DA when using the spectra pre-processed with smoothing by 7-point window moving mean and baseline offset correction, classifying correctly 100% of the pure goat milk samples and misclassifying only one adulterated sample in the test set. This result reinforces the fact of the selection of intervals by SPA provided a more parsimonious model, with less latent variables than the other models, since it selects only the most relevant and interpretable chemical information. Therefore, the proposed methodology represents a promise, non-destructive, fast, and low-cost tool for screening the authentication of raw goat milk, also helping to support future decisions by the regulatory agencies to prevent this kind of fraud directly in the production local.