2.5.2. Water solubility index
The water solubility index (WSI) of the extrudate was determined
following the method described by Anderson, Conway,
Pfeife, and Griffin (1969) with little modification. The extrudates
were ground and about 2 g (Wos) of the ground extrudate was
placed into a centrifuge tube. Distilled water (25 ml) at 30 C was
added with the sample. After 10 min standing with intermittent
shaking every 2 min, the sample was centrifuged at 4000 g for
15 min (Sorvall GLC-2B General Laboratory Centrifuge, Du Point
Instrument). The supernatant was decanted into a Petri dish and
dried at 105 C overnight. The weight of the dry solid (Wds) was
determined and the WSI (g/100 g) calculated: