1. 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.
2. References:
- Total Fat by Gerber/Teichert method - GEA Niro Method No. A 9 b
- TCVN 5504:2010 - ISO 2446:2008.
3. Scope:
The method is to be used for fat-containing milk powders.
4. Apparatus:
- Balance - sensitivity ± 0,0001 g
- Special butyrometer - scale 0-35% or 0-70%.
- Caoutchouc stoppers.
- Pipettes – 1ml and 10 ml.
- Centrifuge.
- Funke Gerber and rotor Hear A
- Water bath
5. Reagents:
- Sulfuric acid (H2SO4) – density 1.846 ± 0.003 g/ml 90-91% at 20oC.
- Amylalcohol (C5 H12O) ≥ 98%, density 0,811 ± 0,002 g/ml at 20oC.
- Distilled water.
6. Procedure:
6.1 Pour successively into the butyrometer:
- 10 ml sulphuric acid.
- 9 ml distilled water. (must not be mixed with the acid).
- Exactly 2.5g powder.
- 1 ml Amylalcohol.
6.2 Close the butyrometer with the caoutchouc stopper and shake untill the powder is dissolved. Turn the butyrometer upside-down 5 times.
6.3 Boil in water bath for 5 minutes at 65 ± 3o C.
6.4 Spin in the centrifuge for 5 minutes at 65 ± 3o C, (mode “Gerb”)
6.5 Shake for further 1 minutes. Turn the butyrometer upside-down 5 times. Spin in the centrifuge for 5 minutes at 65 ± 3o C, (mode “Gerb”)
6.6 Read result:
Adjust the fat colum by using the stopper, so that it will be in the graduated part of the butyrometer.
7. Result:
Fat content theory is read directly on the butyrometer.
Fat content theory:
Note:
+ A: Read a top fat column
+ B: Read a bottom fat column.
+ f: Fat content theory.
+ X(%): The fat percent.
+ m: Quantity sample