The proteins were removed
by filtration. Distilled water was used to wash the residue to neutral.
Then the shrimp shell residue was subjected to the above program for
two times. 250 ml of 95% and absolute ethanol were sequentially used
to remove ethanol-soluble substances from the obtained crude chitin
and to dehydrate. An air oven was taken to dry the chitin at 50 °C
overnight.