Samples of 3 g (±0.2 g)
were weighed (W1) and pressed manually between two layers
of filter paper (Whatman No.1), which were then placed at the
bottom of 50 ml centrifuge tube padded with extra filter paper
and centrifuged at 5000 rpm for 10 min. Immediately after
centrifugation, the samples were reweighed (W2) and the
Ew % was calculated as follows