Relationship between freezing point and raw ewes’ milk components as a possible tool for estimation of milk adulteration with added wate

Milk adulteration with added water is controlled by freezing point depression (FPD) determination. The aim of this study was to evaluate the suitability of an alternative method for FPD equivalent (FPD-E) measurement and to estimate the basis for FPD cut-off value (to identify milk adulteration with added water) for ewes’ milk. Raw bulk ewes’ milk samples (n = 811) from Slovakia were analysed for FPD, FPD-E and composition in 2014. Influence of season and lactation was significant for all milk indicators. The mean FPD of bulk ewes’ milk samples was –0.559 °C ± 0.029 °C. The FPD cut-off value can be in the range close to –0.511 °C (mean + standard deviation × 1.64, one-sided 95% confidence interval). An extent of 89.4% of the variability in FPD-E could be explained by variations in FPD. The total correlation coefficient was 0.945 (p < 0.001) and high correlation was also for FPD greater than –0.511 °C (0.992, p < 0.001). This could be explained by high correlations between FPD and milk components: –0.228 (p < 0.01) for fat, –0.231 (p < 0.001) for proteins, –0.219 (p < 0.001) for lactose, –0.497 (p < 0.001) for non-fat solids and –0.341 (p < 0.001) for total solids. Determination of FPD-E in ewes’ milk can be an effective tool for estimation of milk adulteration with added water.