Water Determination in Ground Coffee by Karl Fischer Titration

Roasted coffee releases the water it contains extremely slowly. The residual moisture is tightly bound at cellular level so the results of Karl Fischer (KF) titration at room temperature are too low.

Two series of tests were carried out as a result of this experience:

  1. Extraction of the water and subsequent titration of an aliquot.
  2. Titration in boiling methanol.

An additional series of dry loss at 130°C has shown that a certain part of water does not release even after 20 hours. Titration of the remaining dried coffee resulted in a water content of still 0.4%.

Roasted coffee releases the water only incompletely using loss of drying or the direct KF-determination in methanol. Long-term extraction at elevated temperature helps completing water extraction. Nevertheless, KF titration in boiling methanol gives the best extraction and most reliable results.

Download the full Laboratory Report for Ground Coffee (L 061 + L 062) here

Your shopping list:

Volumetric reagents: Water Standards: Auxiliaries:
34805 HYDRANAL-Composite 5
34741 HYDRANAL-Methanol dry
37817 HYDRANAL-Methanol Rapid34801 HYDRANAL-Titrant 534800 HYDRANAL-Solvent
34425 HYDRANAL-CRM Water Standard 10.0
34426 HYDRANAL-CRM Water Standard 1.0
34424 HYDRANAL-CRM Sodium Tartrate Dihydrate
34241 HYDRANAL-Molecular Sieve 0.3 nm34788 HYDRANAL-Humidity Absorber

 

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Honeywell Research Chemicals
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