Solubility
The solubility of chitosan is one of important parameters for quality of chitosan, where higher solubility will produce a better chitosan. There are several critical factors affecting chitosan solubility including temperature and time of deacetylation, alkali concentration, prior treatments applied to chitin isolation, ratio of chitin to alkali solution, and particle size. The solubility, however, is controlled by the degree of deacetylation and it is estimated that deacetylation must be at least 85% complete in order to achieve the desired solubility (No et al., 1995). The solubility of chitosan obtained in this study was ranged from 48.3 % to 97.65% with significant difference with respect to NaOH concentration. Deacetylated with 40% and 50% NaOH showed lower solubility which is due to lower DD value. Proportionally increase in solubility was observed with increasing deacetylation degree. Shrimp shell chitosan samples treated with 50% and 60% NaOH were found to have excellent solubility ranging from 96.01% to 97.2% with no significant difference (Table 3). Brine and Austin (1981) noted that lower solubility values suggested incomplete removal of protein and acetyl group. Since solubility of chitosan depends on the removal of acetyl group from chitin, therefore the lower ออ value could adversely interfere with the results.