Development of Karl Fischer Reagents

III-2. Foodstuffs
5. Dairy Products, Fat Products
Because of their high moisture content, most dairy products are titrated
directly using the volumetric method. A sugar-type dehydrated solvent
is normally used as the titration solvent. However, products that have
fats as their principal ingredients, such as butter, are dissolved in an oiltype
dehydrated solvent for titration. When volumetric titration is used
for fat products they are dissolved in an oil-type dehydrated solvent.
The moisture content of vegetable oils, which contain little water, can be
measured more accurately using coulometric titration.
If a product will not dissolve readily in the electrolyte, the addition of
chloroform to the anolyte (equivalent to 20% by volume of anolyte) will
allow the substance to dissolve for repeat titrations.
The moisture vaporization method can be used for samples of these
types. However, the conditions must be determined with care. As a
general rule, a heating temperature in the 110-180°C range is used.
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Key Points
[Examples of Measurement]
(1) Volumetric titration
Reagents used:Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX, OL II, SU (or MS, CM, FM) 25-50ml
Substance
Dehydrated
solvents
Sample Quantity
(g)
Measurement Value
(mg)
Moisture Content
(%)
Powdered milk General-use 0.0572 2.64 4.56
Cream cheese " 0.0485 25.04 51.6
Natural cheese " 0.1143 72.16 63.1
Milk powder Sugar-type 1.0888 30.55 2.81
Condensed milk " 0.0730 19.42 26.6
Fresh cream " 0.1142 16.74 14.7
Powdered cheese " 0.1269 5.43 4.28
Meat extract " 0.1067 18.59 17.4
Rapeseed oil Oil-type 4.6163 0.51 110ppm
Butter " 0.0303 4.25 14.0
Margarine " 0.0970 15.49 16.0
Sugar-type dehydrated solvent should be heated to 40 � C before use in
titration.