Determination of Water Content in Cranberry juice powder Using Karl Fischer Titration

Product Group

Foodstuffs

General Information concerning the product group

Foodstuffs

Foodstuffs encompass the most diverse products. Depending on whether carbohydrate-rich, fatty or proteinrich substances are under investigation, different working techniques are favourable. Complex matrices that dissolve slowly, or where the water can only be slowly extracted, necessitate the use of solubilisers. In addition, titration under heating and the application of a homogeniser to accelerate water release are expedient.

Special Information concerning the sample and the methods

The dissolution of juice powder in methanolic KF solvents is often inadequate. For complete extraction of water titration under warm conditions (50°) is favourable.The use of a homogeniser is recommended as well. The coulometric method can only be applied in combination with KF oven technology. For the release of water a temperature of 120 °C is recommended (disintegration at higher temperatures).

Titration one component system

Reagents:

Titrant
188005 Aquastar™ - CombiTitrant 5 - One component reagent for volumetric Karl Fischer titration, 1 mL = approx. 5 mg water

Solvent
50 mL 188009 Aquastar™ - CombiMethanol - Solvent for volumetric Karl Fischer titration with one component reagents, max. 0.01 % water

Titration Parameters:
Stirring time: 2 min
Temperature: 50°C
Default coulometer settings for cell with diaphragm:
For end point indication, e.g.:
I(pol) = 5 - 10 µA, U(EP) = 50 - 100 mV
Stop criterion: drift < 20 µg/min

Sample size:
0,1 - 0,3g

Procedure:
The titration medium is first placed into the cell, heated up to 50°C and titrated dry by means of the titrant. Then the sample is added from a weighing boat (exact sample weight determination by weighing of weighing boat before and after addition) and the titration is started. For dissolution a stirring time of 2 min (optionally under the use of a homogeniser) is recommended.

Materials

     
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