LABEC M-MIA-LA - Manual (Page 72)

Ultrasonic milkanalyser
Operation manual 04.11.09 70/107
3. Sampling
Samples from milk, whey or buttermilk are taken with metal or glass pipe (dry,
clean and stainless-steel) with diameter at about 10 mm, which is slowly
dipped till the bottom of the vessel and its upper end remains open. In this
way it is filled with milk simultaneously with its dipping. When the pipe is
taken out of the vessel its upper end has to be tightly closed with a thumb.
For a bigger reliability of the analyses results it is recommended the quantity
of the taken sample to be no less than 200 ml.
Cream sample is carefully well stirred in order not to form foam. For taking a
medial sample from milk-cans and tanks a sample pipe is used. Stuck to its
outer surface cream has to be removed by using filter paper, napkin or clean
cloth, preventing in this way the proportionality between the samples and the
total amount of the cream to be disturbed.
4. Sample preservation
The vessels where the samples will be put have to be clean, dry, glass, metal
or from other suitable material, to be tightly closed with rubber or other
stopples. The stopples not to absorb water and fat and not to influence the
analyses sample content.
In summer the sample fills up to the top the vessel, but in winter – at least 3/4
from the vessel’s volume. Each sample for analyses has to be labeled and
described in a way not allowing to be mixed up.
The samples are stored in conditions, assuring temperature, corresponding to
the requirements for storing such kind of product (advisable – 1
o С).
If there is a need of longer sample storing they have to be preserved; the
most commonly used preservative is potassium dichromate (K
2
Cr
2
O
7
) - 1 g
for 1 000 ml. The samples have to be stored in a cold and dark place after the
preservation. Have in mind that during the analyses the results for SNF% will
be increased with 0,1 %. After adding the preservative the sample has to be
well stirred.
Do not make analyses if the acidity of the milk is more than 25 o T for cow and
28 o T for sheep milk.
5. Preparing the samples for analyses
Milk – raw and thermally treated