physicochemical and functional properties of crawfish chitosan as ...

degradation of the chitosan structure occurs. The DD process is a very harsh treatment with
concentrated sodium hydroxide (40-50%) usually at 100 o C or higher for 30 min.
On the other hand, comparing DMPCA and DPMCA, the DMPCA showed viscosity of
131.8 cP whereas 403.3 cP for DPMCA. One is almost tempted to believe that reversing
demineralization (DM) and deproteinization (DP) process during the chitosan production seems
to have no effect on the characteristics of crawfish chitosan, but the results (Table 5) otherwise
showed significant differences between the two samples (DMPCA vs. DPMCA).
There are some factors affecting viscosity during the production of chitosan such as the
degree of deacetylation, molecular weight, concentration, ionic strength, pH, and temperature,
etc. Moorjani et al. (1975) reported that chitosan viscosity decreased with increased time of
demineralization. The viscosity of chitosan in acetic acid tends to increase with decreasing pH
but decrease with decreasing pH in HCl. Intrinsic viscosity of chitosan is a function of the degree
of ionization as well as ion strength (Bough et al., 1978). Deproteinization with 3% NaOH, and
elimination of the demineralization step in chitin preparation, decreased the viscosities of the
final chitosan samples (Bough et al., 1978). Moorjani et al. (1975) stated that it is not desirable to
bleach the material at any stage since bleaching considerably reduces the viscosity of the final
chitosan product.
4.8 Solubility
All five crawfish chitosan samples and the commercial chitosan, Vanson75, demonstrated
an excellent solubility ranging from 93.3 to 94.3% with no significant difference (Table 5), while
the commercial chitosan, Sigma91, showed slightly lower solubility (87.8%). Brine and Austin
(1981) noted that lower solubility values suggest incomplete removal of protein. Since the
chemical basis of this method is based on the reaction with the amino group, the presence of
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