physicochemical and functional properties of crawfish chitosan as ...

process of converting a polymer into a monomer or a mixture of monomers as defined by the
(IUPAC Compendium of Chemical Terminology 2nd ed., 1997). Kurita (1998) noted that
chitosan solubility’s stability is poor above pH 7 and at a higher pH, precipitation or gelation
occurs. In addition, chitosan solution forms poly-ion complex with anionic hydrocolloid, giving
rise to a gel formation, which was also observed for DAPMC in this study. Though high
temperature over 280 o C causes thermal degradation of chitosan and thus polymer chains rapidly
break down, this was not the case in this study as very low temperature (121 o C) was utilized. The
probable explanation of what observed in this study is the rapid depolymerization of chitosan
hydrochloride. Since chitosan polymer contains hydroxyl and amino, polar groups in its
molecular structure, it possesses thermodynamic instability. For DAPMC, after harsh reaction of
deacetylation, the shell was reacted with HCl, presuming that hydrogen chloride liberated in the
probe attacks the β-glycosidic links between the monomer units, causing gelation and then
depolymerization.
4.1.1 Formation to Gel-like Mass
After deacetylation (DA) and demineralization (DM) step, the shell was immediately
washed using the tap water to remove HCl. The pink colored wet shell (DAPM) suddenly
transformed into a viscous gel as seen in Figure 5.
Figure 5. Non-Powdered (Gel-like) Chitosan
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