RELATIONSHIP BETWEEN ALCOHOL STABILITY OF COWS MILK AND SOME COMPONENTS AND FACTORS OF PRIMARY PRODUCTION

Resistance of proteins to precipitation is an important precondition for UHT heating, high milk pasteurization, and production of condensed milk. For predicting the stability of proteins, thermal stability test is being used which can be replaced by the alcohol test. 2552 bulk samples of milk have been collected from cows of the Bohemian Pied breed with a different share of improving Aryshire, Red Holstein, and Black Pied Lowland land breed with different levels of absorptive crossing from the Bohemian Pied breeds having a share of the Holstein breed. Samples of non-preserved milk were measured as to the content of fat M, proteins (B), lactose (L), solids-non-fat (TPS), and urea (M) and the value of actual acidity (pH), titration acidity (SH), and conductivity (gamma), as well as somatic cell count (SB) have been assessed. The alcohol stability was defined as the consumption of 96 % ethanol added to 5 ml milk until a distinct precipitation (AS) occurs. Tab. II gives basic statistical data. The results obtained show that the milk samples had very good characteristics and were collected from healthy cows. Somatic cell count was 164 thous./ml, protein content 3.25 %, lactose content was high - 4.86 %. The value of alcohol stability was found to be 5.40 ml. Correlation coefficients between alcohol stability and other parameters of bulk milk samples are given in Tab. III. Besides SH, AS is in a lower but significant relationship to all indices observed; a negative relationship was found between AS and the content of T, B, SB, gamma (r = -0.09, -0.08, -0.08, -0.17). Alcohol stability deteriorates with an increase in pH (r = 0.11), positive correlation coefficients were stated between AS and L (r = 0.30), and AS and M (r = 0.12). Tab. IV, significance of the effect from variance analysis is given: effect of month on the indices observed was in all cases statistically significant. The content of B was lowest in August (3.03 %) with a subsequent increase in September and October (3.38 %). The value of SB fluctuated distinctly, with a minimum m February (130 thous./ml). The lowest urea content was found in April, a maximum content in July (38 mg/100 ml) and a decrease to 27 mg/100 ml in October. The highest alcohol stability (6.60 ml) was noted between June and August, while it was lowest in December (4.60 ml) - Fig. 1. As to the effect of breed, a non-significant relationship to M and SH has been found, other components and properties have been significantly affected (with the exception of SB). Red Pied dairy cows showed lower SB (154 thous./ml), compared with 183 thous./ml in Black Pied cows which probably corresponds with the findings of higher AS values in the Red Pied cattle (Fig. 2) - 5.50 ml in comparison to 5. 10 ml. The effect of region on individual indices (except SH) was significant (Fig. 3). Higher values of the content of T, B, L, M, TPS, SB, pH, and AS were found in the maize growing region. The effect of lactation order (Fig. 4) was significant for all components and properties except M, T, and pH. First-calf heifers showed lower SB compared to older cows (141 thous./ml against 173 thous./ml). A higher AS of the milk protein (5.60 ml against 5.30 ml) could probably be in correspondence with a better health condition.