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GEA Niro Method No. A 1 a |
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Revised: September
2006 |
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1.
Definition
The moisture content of a powder is the
loss in weight (%) after oven drying at 102°C until constant weight is
obtained.
2.
Scope
This is an accurate standard method which
may be used for milk powder and all other powdered dairy products which do not
contain crystallized lactose (α-lactose-monohydrate).
3.
Principle
The sample is dried by oven drying to
constant weight at 102°C ± 2°C for 2 hours. The oven drying is repeated until
the two successive weighings do not differ more than 0.5 mg.
4.
Apparatus
4.1 Drying oven,
with thermostat and without forced air circulation.
4.2 Analytical
balance, sensibility ± 0.1 mg.
4.3 Desiccator
with colour-indicating desiccant (e.g. silica gel).
4.4 Weighing
dishes with lid.
5.
Reagents
None
6.
Procedure
6.1 Dry weighing
dish with open lid in the oven, and cool it in
desiccator.
6.2 Weigh the
empty dish (a), add approx. 3 g of powder and weigh again
(b)
6.3 Place the
loaded dish with open lid in the oven at 102°C ± 2°C for
2
hours.
6.4 Cool closed
dish to room temperature in desiccator, and weigh (c).
6.5 Continue
drying the loaded dish with open lid in the oven at 102°C
± 2°C for 1
hour.
6.6 Repeat the
cooling 6.4 and weigh again (c).
6.7 Repeat 6.5
until weight (c) is constant (i.e. until two successive weighings differ less
than 0.5 mg)
7.
Calculation
&nb
sp; a = weightof empty
dish
b = weight of dish +
powder
c = weight of dish + dried
powder
8.
Reproducibility
± 0.1 %
9.
Remarks
A sample for moisture determination has to
be handled carefully in order to avoid evaporation or prevent adsorption.
10.
Literature
• GEA Niro Research
Laboratory
• IDF Standard № 26:2004 /
ISO Standard № 5537:2004
•
De Knegt, R.J. and Brink, H.v.d.: Improvement of the drying oven method
for the Determination of the Moisture Content of Milk Powder. Int. Dairy
Journal, 8, 1998, pp. 733-738.