RELATIONSHIPS OF FERMENTATION AND OTHER TECHNOLOGICAL CHARACTERISTICSTO SELECTED PARAMETERS OF MILK

Milk fermentation test is performed to determine the usability of milk for the production of fermented milk products. Its result depends on many factors involving the presence of inhibitory substances, basic mi lk composition and the way of performing the test itself. About 220 bu lk milk samples were taken in monthly intervals during one-year observ ation; fermentation was evaluated by help of so called yoghurt test, o ther technological characteristics were also evaluated and their relat ionships to basic milk composition were determined. Tab. I shows basic statistical data; average value of milk fermentation indicated a rela tively negative result 21.8 x 2.5 mmol/l with regard to the requiremen ts of the standard CSN 57 0529. It can also be deduced from the averag e somatic cell counts (339 thousand/ml) that milk was collected in cow sheds with worse health situation. Urea concentration in milk was 24.5 mg/100 ml. Macroelement concentrations were also determined in the sa mples (Tab. II), e.g. magnesium concentration was low (98.8 mg/kg milk ). Significance of differences between the characteristics in two grou ps classified according to fermentation below the limit 25 x 2.5 mmol/ l and above it are shown in Tab. III. The difference was significant f or the content of proteins, nonfat solids and for the higher values of fermentation. Curd firmness was found to be highest. Variations in so me parameters were followed throughout the year (Fig. 1). Yearly ferme ntation values were low, except January and summer months, urea concen tration was also highest in summer. Somatic cell counts were increasin g throughout the year to reach the highest values in September. Tab. I V shows significant coefficients of correlation between the components and characteristics of bulk milk of cows, while Tab. V indicates the correlations between macroelements and other characteristics. Coeffici ents of correlation between fermentation and lactose (r = 0.19), nonfa t solids (r = 0.19), curd firmness were positive (r = 0.19), but they were negative for conductivity (r = -0.26), curd quality (r = -0.16) a nd sodium (r = -0.17) and phosphorus (r = -0.23) concentrations. Milk titratable acidity showed a positive relation to the content of the se parate components (fat, proteins and lactose). It showed a negative re lation to sodium concentration and a positive relation to potassium co ntent. A negative relationship between lactose concentration and somat ic cell counts (r = -0.36) was confirmed, nonfat solids showed a posit ive relation to curd firmness, milk acidity, and to the separate compo nents following titratable acidity fractionation. A negative relations hip was confirmed between curd firmness and coagulation time (r = -0.4 7) while there was a positive relationship between curd firmness and c alcium content (r = 0.28). Alcohol stability was influenced by variati ons in characteristics and milk composition to the least extent. Tests to determine the effects of residual quantities of disinfectants and cleaning agents were also performed. As shown, they should not influen ce the technological process on condition that the hygienic regime is observed. Low objectiveness of this test can be another cause of milk low fermentation.