LABEC M-MIA-A - Manual (Page 66)

Ultrasonic milk analyser
transparent layer. The volume of this layer is measured in the divided part of
the butyrometer.
This is quick, easy method with sufficient accuracy. We recommend it for
usage. For more detailed description see Appendix Methods.
2.1.2. Milk density determination
А/ With picnometer and Mor-Vestval scales
This is the most exact method for determination of milk and its derivatives’
density.
B/ with aerometer (lacto-density-meter)
Compared with the above method this is quick and easy readable with
satisfactory accuracy. We recommend it. For more detailed description see
Appendix Methods.
During the lactation period and under the influence of different zoo
engineering factors the density of the different milk kinds varies in the
following bounds:
Milk kind Minimum Maximum Average
Cow 1,027 1,033 1,030
Buffalo 1,026 1,032 1,029
Goat 1,027 1,033 1,030
Sheep 1,031 1,040 1,034
2.1.3. Determination of total proteins
А/ Kjeldahl method
Heating with concentrated sulphuric acid in the presence of catalyst
mineralizes a definite volume of the milk sample. The liberated ammonium
combines with the sulphuric acid and forms ammonium sulphate. After adding
surplus soda caustic ammonium is liberated. When distilled it combines with
the boronic acid. The quantity of the combined ammonium is determined by
titration with acid with determined titer. From the combined with the
ammonium acid the initial nitrogen content is determined, and also the
proteins in the milk.
B/ Titration with formalin
Formalin, added to the milk, combines with the amino group in the protein’s
molecule and forms methyl groups, which have no alkaline reaction. Milk
acidity increases by the liberated carboxylic groups, which are titrated with
soda caustic solution. The used volume soda caustic is proportional to the
protein content in the milk.
Operation manual MRC.VER.01-02.10