physicochemical and functional properties of crawfish chitosan as ...

protein contaminants remaining in the sample during the analysis process could adversely
interfere with the results. The commercial chitosan, Sigma91, had the highest N-residue (8.5%)
(Table 3). This implies that the deproteinization process on our five samples might have been
nearly complete but Sigma91 still had some protein remaining or other impurities.
4.9 Bulk Density
According to Cho et al. (1998) and Brine and Austin (1981), the bulk density of crawfish
and commercial chitin and chitosan varies, and this can be attributed to species or sources of
chitosan and the methods of preparation.
The bulk density reported for chitin from shrimp and crab is 0.06 and 0.17 g/ml,
respectively (Shahidi and Synowiecki, 1991), indicating that shrimp chitin is more porous than
crab chitin. Krill chitin was found to be 2.6 times more porous than crab chitin (Anderson et al.,
1978). In the study of No et al. (1995), the bulk density of commercial crab chitosan ranges from
0.18 – 0.33 g/ml, indicating up to 1.8 times difference in porosity.
Rout (2001) reported the bulk density of chitin and chitosan from crawfish shell to be
very high (0.39 g/cm 3 ). This may be due to the particle size and porosity of the material before
treatment. But once crawfish shell had been demineralized or deproteinized or both there were
minor variations in bulk density among chitin and chitosan produced.
The untapped bulk density of crawfish chitosan samples was in the range of 0.16 – 0.19
g/ml and those of the tapped samples were between 0.20- 0.24 g/ml (Table 5). This indicates that
our crawfish chitosan samples are not that significantly different among themselves and are in
the range reported by No et al. (1995). But Vanson75 had a lower bulk density of 0.17 g/ml and
was more porous than the others. Cho and No (1999) noted that lower bulk density may indicate
that the chitosan is more porous and may have been subjected to a lower alkali concentration
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