LABEC M-MIA-LA - Manual (Page 59)

Ultrasonic milkanalyser
Operation manual 04.11.09 57/107
APPENDICES
APPENDIX 1 METHODS
1. Determination of milk's density
1.1. General
Milk density is defined as relation between the mass of definite milk volume at
temperature 20
o
С and the mass of equal volume distilled water at
temperature 4 o С.
Density, alone, could not be used as a control parameter at milk quality
control. Using the density the tentative figures for the SNF and salts could be
determined.
1.2. Sampling and preparation for analyses
Sampling milk or other milk derivatives and their preparation for analyses is
done according corresponding Appendices.
Milk density is determined not earlier than 2 h after milking. The milk must be
with temperature from 10 to 25
o С.
Before determination of density the milk must be well stirred. To avoid foam
formation, it has to be carefully poured on the cylinder’s walls. The cylinder
must be slightly tilted.
Before taking the readings the cylinder, with the milk must be placed on an
even surface, facing the light, so the readings could be easily seen.
1.3. Basic principles.
The density of the milk is determined using aerometer, also called lacto-
density-meter (milk density meter) and is expressed with a number,
representing milk density meter degrees, decreased 1000 times or only with
milk density meter degrees.
1.4. Necessary devices and reagents
- Aerometer /lacto-density-meter, milk meter/.
- Cylinder – with inner diameter not less than 5 сm, and length, corresponding
to the dimensions of the lacto-density-meter.
- Ammonium with preliminary defined relative density.
1.5. Making the determination:
Dry and clean, the lacto-density-meter is slowly dipped in the milk till division
1,030, and then is left in free-floating state. The lacto-density-meter must not
touch the cylinder’s walls and to be on at least 5 mm from them.
When taking the readings the eyes must be on one and the same level with
the meniscus. The reading is done in the meniscus’ upper end with accuracy
till 0,0005, and the temperature – with accuracy till 0,5
o С.