the typical colonies of coagulase-positive staphylococci for 24±1 hours in the form of
black or grey, shiny and bulging, 1.0−1.5 mm in diameter (48±1 hours – 1.5–2.5 mm
in diameter) and surrounded by clean area and has opalescence rings in 24±1 hours of
incubation.
Table 4 Indices of advanced horizontal method of coagulase-positive
staphylococci detection in milk and dairy products (example № 3)
№
Studied samples of
milk and dairy
products
Detection of coagulase-positive staphylococci by color an dsize of
colonies (example № 3)
Numb
er of
sample
s
The presence of
colonies of coagulase-
positive staphylococci
Numb
er o f
sample
s
The absence of
colonies of
coagulase-positive
staphylococci
1
Raw Milk (fat
content is 3.7%),
n=10
n=2
There are
Typical colonies of
black or grey, shiny
and bulging, with a
diameter of 1.0 −1.5
mm in 24±1 hours (in
48±1 hours – with a
diameter of 1.5−2.5
mm) surrounded by a
clean area, which in 24
hours of incubation has
opalescence rings
n=8
Atypical colonies of
shiny black with/or
without narrow white
edge, a pure zone is
absent, opalescence
ring is absent or
barely noticeable;
grey colonies without
clean areas
2
Past eurized milk (fat
content is 2.8%),
n= 10
n=0
n=10
3
Cream, n=6
n=3
n=3
4
Past eurized Cream,
n=5
n=0
n=5
5
Curds, n=6
n=1
n=5
6
Cheese, n=7
n=1
n=6
7
Melted cheese, n=8
n=1
n=7
8
Butter, n=9
n=2
n=8
9
Spread, n=6
n=2
n=4
The results of the research showed that the typical coagulase-positive
staphylococci were identified in 24±1 and 48±1 hours at the temperature of 35±1 °C in
the following samples of milk and dairy products: 3 samples of cream; 2 samples of
raw milk, butter, cream and spread; 1 sample of curd, cheese and melted cheese. The
typical colonies of coagulase-positive staphylococci were not found in pasteurized
cream and pasteurized milk.
These results were steady and reliable, so these indices can be used in determining
the safety of milk and dairy products. In addition, it should be noted that the method is
economical, simple in execution, but its results give specific quality indicators of
typical colonies of coagulase-positive staphylococci of black or grey color, brilliant
and bulging, 1.0−1.5 mm in diameter (in 48±1 hours – 1.5−2.5 mm in diameter) and
surrounded by clean area, which has opalescence rings in 24±1 hours of incubation.
We consider this method to be a high-quality strategy for improving the horizontal
method of coagulase-positive staphylococci detection in milk and dairy products on an
equal basis with other methods of safety determination (determination of the total
number of microorganisms, the determination of coliform bacteria, Listeria,
Salmonella) [5].
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