Determination of Water Content in Ice Cream 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

Due to the inadequate solubility of ice cream in methanolic KF solvents the addition of chloroform is necessary. The non-homogeneous distribution of water as well as the small sample size require good homogenisation for KF titration prior to sampling. As an alternative, it is possible to carry out an external extraction with a suitable solvent. For the KF titration an aliquote of the sample is withdrawn. The result must be corrected for the blank value of the solvent.

Titration one component system

Reagents:

Titrant
188005 Aquastar™ - CombiTitrant 5 - One component reagent for volumetric Karl Fischer titration, 1 mL = approx. 5 mg water
or
188002 Aquastar™ - CombiTitrant 2 - One component reagent for volumetric Karl Fischer titration, 1 mL = approx. 2 mg water

Solvent
50 mL 188008 Aquastar™ - CombiSolvent - Methanol-free solvent for volumetric Karl Fischer titration with one component reagents
and
35 mL / 15 mL 188009 / 102445 Aquastar™ - CombiMethanol / Chloroform - Solvent mixture for one component titration

Titration Parameters:
Default titration settings, e.g.:
I(pol) = 20 - 50 µA, U(EP) = 100 - 250 mV
Stop criterion: drift < 20 µL/min

Sample size:
approx. 0.04g

Procedure:
The titration medium is first placed into the titration cell and titrated dry by means of the titrant. Then the sample is added with a syringe (exact sample weight determination by weighing of syringe before and after injection) and the titration is started. For weigh-in quantities of approx. 0,04g the solvent must be changed after 4 - 6 measurements.

Materials

     
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