2.4.4. Water absorption index (WAI) and water solubility index (WSI) measurement
Two centrifuge tubes were weighed separately with individual weights. 2.5 g of sample was then put in each tube.
30 mL of distilled water were added and stirred with sample to avoid lumps.
The tubes were closed and placed in the water bath with 25 °C for 20 min.
Those tubes were centrifuged at 5000 rpm for 10 min.
The water was then decanted from the tube without loss of solids.
Finally, the tube and residues were weighed out. The WAI was calculated as following equation: