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GEA Niro Method No. A 11 b |
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Revised: September 2005 |
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1.
Definition
Particle density (g/ml) is defined
as the mass of particles having a total volume of 1 ml.
Occluded air (ml/100g) is defined
as the difference between the volume of a given mass of particles and the
volume of the same mass of air-free solids.
Interstitial air (ml/100g) is
defined as the difference between the volume of a given mass of particles and
the volume of the same mass of powder tapped 100 times (100x tapped
powder).
2.
Scope
This method may to be used for all
powders.
3.
Principle
The weighted amount of powder is
added to petroleum ether in a measuring cylinder. The weight of the powder
divided by the volume increase of the petroleum ether gives the particle
density.
4.
Apparatus
1. Analytical balance, capable of weighing to 0.1
mg.
2. Calibrated 100 ml measuring cylinder with glass
stopper.
3. Rubber spatula.
4. Pipettes – 10 ml
and 50 ml
5.
Reagents
Petroleum
ether.
6.
Procedure
1. Weigh out 25 g powder into
the measuring cylinder.
2. Add 50 ml petroleum ether
with a pipette and shake the measuring cylinder gently until all the powder is
suspended.
3.
Using the rubber spatula,
scrape down all the powder particles on the wall of the measuring cylinder.
Rinse with a further 10 ml of petroleum ether from a
pipette.
4. Read the total volume of
petroleum ether with suspended powder.
5. Determine the moisture
content (Method A1a), the fat content (Method A9a) and the 100x tapped powder
bulk density (Method A2a).
7.
Result
8.
Reproducibility
Particle
density ± 0.03 g/ml
9.
Remarks
1. When calculating powder of
different compositions, the density and the amounts of the constituents must be
taken in consideration. For this purpose, the following values may be
used.
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Powder material, moisture free
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Density at 20°
C |
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Whole milk powder (28%
fat) |
1.280 |
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Non-fat milk
solids |
1.520 |
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Milk fat in
powder |
0.940 |
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Ca-caseinate phosphate
complex |
1.390 |
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Amorphous
lactose |
1.520 |
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Beta-lactose |
1.590 |
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Alpha-lactose
monohydrate |
1.545 |
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Anhydrous
alpha-lactose |
1.545 |
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Spray dried whey
powder |
1.580 |
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Residual whey
components |
1.800 |
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Demineralized whey
powder |
1.525 |
10.
Literature
·
GEA Niro Research Laboratory
·
Buma T.J.: 'The true density of spray milk powder and of certain
constituents' (Netherlands Milk and Dairy Journal, 1965, 19, pp.
249-265)