Raman Spectroscopy as a fast tool for whey quantification in raw milk

Abstract

Adulteration of raw milk with whey is difficult to evaluate because both have great physical and chemical similarities. Herein, we proposed a rapid and cost-effective method to detect and quantify the presence of whey in milk using Raman spectroscopy, while dispensing any step of sample preparation. Principal Component Analysis (PCA) was performed for outlier detection and Partial Least Squares regression (PLS) for prediction of whey content. Since single vibrational modes have been not identified in order to discriminate the different levels of whey addition, we proposed a calibration model from the full Raman spectra using PLS regression. We explored the idea that small differences in spectroscopic data could be useful in this evaluation by using multivariate chemometric methods. As result, the correlation coefficient between the Raman method and the experimental values was R² = 0.988 for the validation samples. A paired t-test revealed a p-value greater than 0.5, pointing out that no significant statistical differences between the proposed Raman method and the reference values. The approach proposed in this study shows to be quite useful for the evaluation of milk adulteration by whey addition, thus contributing to quality control of milk in dairy industry.