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

Abstract

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.

Raw Cow Milk Protein Stability under Natural and Technological Conditions of Environment by Analysis of Variance

“…A lack of information in the data file occurred, which was consequently limited to the complete form of results. Some monitored milk indicators have usually confirmed an absence of normal data frequency distribution, such as hygienic and microbiological indicators (SCC, total count of mesophilic microorganisms (TCMM), count of coliform bacteria (CCOL)) and also HS, according to the results of previous studies [ 31 , 32 , 33 , 50 , 51 , 52 , 53 , 54 ]. Further, because of this reason, the logarithmically transformed (log, on a decimal basis) results were used for the statistic evaluation, including an application of relevant geometric means.…”

“… IND = indicator; n = sample number; x = arithmetic mean; xg = geometric mean; s d = standard deviation; R 2 = coefficient of determination by linear model in analysis of variance; p = probability of zero hypothesis; a in 10 3 ·mL −1 ; b in 10 3 CFU·mL −1 (CFU colony forming unit); c in CFU·mL −1 ; d in minutes; used units and explanation of abbreviations of milk indicators are in Table 2 ; some figures in table were used also previously [ 31 , 32 , 33 ] in different evaluation of milk heat stability (HS). …”

“… IND = indicator; figure means probability of zero hypothesis by F value; normal letters, statistic significant; italics letters, insignificant; the explanation of abbreviations of milk indicators (x axis of this table) and environmental and technology farm factors (y axis) is in Table 2 and Table 3 ; some figures in table were used also previously [ 31 , 32 , 33 ] in different evaluation of milk heat stability (HS). …”

“…In previous studies, we dealt with the relationships between milk indicators and the season to HS, and also the effect of feeding silage from legume-cereal mixtures on HS [ 31 , 32 , 33 ]. While the milk components of the bulk tank samples did not correlate much with the HS, in terms of simple correlations, closer relationships were shown between the composition of the milk and the HS, taking into account the effect of the season.…”