Attempts to determine amount of fat in milk samples containing less than 1% fat resulted in unacceptable high quantification errors due to the weakness of respective bands in the Raman spectra.
3.2. Repeatability of quantification
In a separate step, a set of 64 samples of commercial milk samples containing 3.2% of fat were analysed using the developed calibration models (the scores plots of PCA modelling for these samples are shown in Fig S4 of supplementary material). Milk components were quantified with the mean relative error values in the range 4.2–5.8% for fat, 3.8–4.6% for protein, 3.9–4.8% for carbohydrates and 2.4–2.8% for dry matter (Fig. S5 of supplementary material).