2.2.1. Demineralization
Calcium carbonate constitutes the main inorganic component of the shells. To remove the calcium carbonate, only dilute hydrochloric acid was used to prevent hydrolysis of chitin (No et al.,1995). The hydrochloric acid concentrations ranged from 0.25 to 2 M and the reaction time was varied from 10 to 120 min. The ratio of dried shells to acid solution used during the extraction of chitin ranged from 1/10 to 1/30 (w/v). The experiments were carried out at room temperature under constant stirring of 150 rpm. The decalcified shells were collected on a 250mm sieve, washed to neutrality with tap water, rinsed with deionised water, and then oven-dried at 80 C overnight. The rate of demineralization was
evaluated by determining ash contents in the solid.