V. Gencurova et al., RELATIONSHIPS OF FERMENTATION AND OTHER TECHNOLOGICAL CHARACTERISTICSTO SELECTED PARAMETERS OF MILK, Zivocisna vyroba, 42(8), 1997, pp. 375-382
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.