Seasonal Correlations Between Heat Stability and Other Raw Bulk Cow Milk Quality Indicators

Heat milk stability (thermostability, TES) is important technological feature which can contribute to create higher added value in the dairy industry. The aim of this paper was to evaluate the seasonal dynamics and relationships of TES to other milk qality indicators in the results of an exceptionally large data set of bulk samples without technological compositional modification and acidity adjustment, just with native raw cow milk. There were carried out 2,634 of TES measurements including other milk indicators during 3 years under controlled farm conditions. Results were processed by polyfactorial linear model of variance analysis and linear and nonlinear regression method. Correlation indexes of seasonal dependence of milk indicators such as fat content (F), crude protein content (CP), lactose monohydrate concentration (L), solids non‑fat content (SNF), total solids (TS), urea concentration (U), F/CP ratio, F/L ratio, milk freezing point (MFP), somatic cell count (SCC), total count of mesophilic microorganisms (TCM) and coli‑form bacteria count (COLI) were significant (P < 0.05 and < 0.01) including TES (r = 0.869; P < 0.01), with the exception of F/CP (P > 0.05). The seasonal dynamics of milk TES values corresponds positively with the trends of U and L. The negative seasonal trends are between milk TES and F, CP, SNF, TS, F/CP, F/L and MFP. Significant (P ≤ 0.1) negative seasonal correlations were between TES and F, CP, TS and F/L (–0.56, –0.55, –0.54 and –0.57). Significant (P ≤ 0.05) positive seasonal correlations were between TES and U and TCM (0.62 and 0.58). Insignificant (P > 0.1) negative seasonal correlations were found between TES and SNF, F/CP and MFP (–0.49, –0.29 and –0.16). Insignificant (P > 0.1) positive seasonal correlations were between TES and L, SCC and COLI (0.44, 0.42 and 0.43). Performed explanation of possible effects of chosen factors on raw cow milk TES can allow efficient selection of raw material for its processing by technological treatment under high temperature into relevant dairy products.