Determination of Water Content in Mayonnaise 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 this substance in methanolic KF solvents the addition of solubilisers (e.g. long-chain alcohols, chloroform) or utilisation of specific KF solvents for fats (e.g. CombiSolvent fats) is necessary. Additionally, titration under warm conditions (50 °C) and/or the use of a homogeniser is favourable. Due to the high water content and the solubility properties the coulometric method is not recommended here.

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 188021 Aquastar™ - CombiSolvent fats - Solvent for volumetric Karl Fischer titration with one component reagents for fats

Titration Parameters:
Stirring time: 180 sec.
Default titration settings, e.g.:
I(pol) = 20 - 50 µA, U(EP) = 100 - 250 mV
Stop criterion: drift < 20 µL/min

Sample size:
0.3 g

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 1 mL syringe without hollow needle (exact sample weight determination by weighing of syringe before and after injection) and the titration is started. For complete dissolution of the sample a stirring time of 180 seconds is recommended.

Titration two component system

Reagents:

Titrant
188010 Aquastar™ - Titrant 5 - Titrant for volumetric titration with two component reagents, 1 mL = approx. 5 mg water

Solvent
40 mL 188016 Aquastar™ - Solvent oils & fats - Solvent for volumetric Karl Fischer titration with two component reagents for oils & fats
and
10 mL 102445 Chloroform - as solubiliser

Titration Parameters:
Stirring time: 180 sec.
Default titration settings, e.g.:
I(pol) = 20 - 50 µA, U(EP) = 100 - 250 mV
Stop criterion: drift < 20 µL/min

Sample size:
0.3 g

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 1 mL syringe without hollow needle (exact sample weight determination by weighing of syringe before and after injection) and the titration is started. For complete dissolution of the sample a stirring time of 180 seconds is recommended.

Materials

     
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