physicochemical and functional properties of crawfish chitosan as ...
physicochemical and functional properties of crawfish chitosan as ...
physicochemical and functional properties of crawfish chitosan as ...
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
process <strong>of</strong> converting a polymer into a monomer or a mixture <strong>of</strong> monomers <strong>as</strong> defined by the<br />
(IUPAC Compendium <strong>of</strong> Chemical Terminology 2nd ed., 1997). Kurita (1998) noted that<br />
<strong>chitosan</strong> solubility’s stability is poor above pH 7 <strong>and</strong> at a higher pH, precipitation or gelation<br />
occurs. In addition, <strong>chitosan</strong> solution forms poly-ion complex with anionic hydrocolloid, giving<br />
rise to a gel formation, which w<strong>as</strong> also observed for DAPMC in this study. Though high<br />
temperature over 280 o C causes thermal degradation <strong>of</strong> <strong>chitosan</strong> <strong>and</strong> thus polymer chains rapidly<br />
break down, this w<strong>as</strong> not the c<strong>as</strong>e in this study <strong>as</strong> very low temperature (121 o C) w<strong>as</strong> utilized. The<br />
probable explanation <strong>of</strong> what observed in this study is the rapid depolymerization <strong>of</strong> <strong>chitosan</strong><br />
hydrochloride. Since <strong>chitosan</strong> polymer contains hydroxyl <strong>and</strong> amino, polar groups in its<br />
molecular structure, it possesses thermodynamic instability. For DAPMC, after harsh reaction <strong>of</strong><br />
deacetylation, the shell w<strong>as</strong> reacted with HCl, presuming that hydrogen chloride liberated in the<br />
probe attacks the β-glycosidic links between the monomer units, causing gelation <strong>and</strong> then<br />
depolymerization.<br />
4.1.1 Formation to Gel-like M<strong>as</strong>s<br />
After deacetylation (DA) <strong>and</strong> demineralization (DM) step, the shell w<strong>as</strong> immediately<br />
w<strong>as</strong>hed using the tap water to remove HCl. The pink colored wet shell (DAPM) suddenly<br />
transformed into a viscous gel <strong>as</strong> seen in Figure 5.<br />
Figure 5. Non-Powdered (Gel-like) Chitosan<br />
42