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GEA Niro Method No. A 9 b |
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Revised: September 2005 |
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1.
Definition
The fat can be separated from
fat-containing milk/milk powder through the addition of sulphuric acid. The fat
content is read directly on a special calibrated butyrometer after
centrifugation.
2.
Scope
The method is to be used for
fat-containing milk powders.
3.
Principle
The fat can be separated from
fat-containing milk/milk powder through the addition of sulphuric acid. The
separation is made by using amyl alcohol and centrifugation. The fat content is
read directly on a special calibrated butyrometer.
4.
Apparatus
1. Balance - sensitivity ± 0.01
g
2. Special butyrometer-scale
0-35% or 0-70%, Teichert, ‘2.5 g lait en poudre’ 65°C
3. Caoutchouc stoppers
4. Pipettes - 1 and 10
ml
5. Centrifuge, Funke Gerber -
1200 rpm, equipped with heating element
5.
Reagents
1. Sulphuric acid,
H2SO4 - density 1.816 ±0.003 g/ml
90-91%, clear, colourless.
2. Amylalcohol,
C5H12O - density 0.811 ±0.002 g/ml
6.
Procedure
1. Pour successively into the
butyrometer:
10 ml sulphuric
acid.
8 ml
distilled water (must not be mixed with the acid).
Exactly 2.5 g
powder.
1 ml
amylalcohol.
2. Close the butyrometer with
the caoutchouc stopper and shake until the powder is dissolved. Turn the
butyrometer upside-down 5 times.
3. Spin in the centrifuge for
15 minutes at 65°C.
4. Shake for further 5 minutes.
Spin in the centrifuge for 15 minutes at 65°C. Adjust the fat column by using
the stopper, so that it will be in the graduated part of the butyrometer. The
fat percentage can then be read directly after spinning again for further 5
minutes.
5. Measurements are carried out
in duplicate.
7.
Result
The fat
content is read directly on the butyrometer and an average value of the two
determinations is calculated. Calculate the result to 1 decimal
place.
;
8.
Reproducibility
± 0.3 % for the 0-35 % scale
± 0.5 % for the 0-70 % scale
9.
Remarks
1. It is important to wear acid
resistant gloves, protection glasses or a protection
shield.
2. Samples containing sugar
must not be analyzed by this method. Sugar can react very violently with
concentrated sulphuric acid and cause an explosion.
3. If the powder is not
dissolved after step 5.2, place it in a water bath at < 65°C until it
is dissolved.
4. If the fat content is
>70%, the procedure is repeated using only 1.25 g of powder instead of 2.5
g, and the result is multiplied by 2.
5. For baby food and whole
milk, a butyrometer with the scale from
0-35% is used. For powders with a
higher fat content, a butyrometer with a scale from 0-70% is
used.
6. If the expected fat content
is close to 1%, or if a higher precision of the fat content is required, use
the Röse Gottlieb Method A 9 a.
7. The sample must be 65°C when
reading the fat percentage. If the centrifuge is not adjusted to the right
temperature, the butyrometer must be heated in a water
bath.
10.
Literature
• GEA
Niro Research Laboratory
• IDF Standard
1C:1987.