physicochemical and functional properties of crawfish chitosan as ...

and elimination of the demineralization step in chitin preparation, decreased the viscosities of
chitosan samples, where as Moorjani et al. (1975) indicated that it is not desirable to bleach the
material at any stage since bleaching considerably reduces the viscosity of the final chitosan
product.
4. Atmosphere
Many scientists have agreed that free access of oxygen to chitin during deacetylation has
a substantial degrading effect on chitosan. Deacetylation in the presence of nitrogen yielded
chitosan of higher viscosity and molecular weight distributions than did in air. However, little
differences in nitrogen and ash compositions were observed (Bough et al., 1978; Lusena and
Rose, 1953; Rigby, 1936).
5. Ratio of Chitin to Alkali Solution
Moorjani et al. (1978) emphasized that the ratio of chitin solids to alkali solution plays a
significant role in determining the quality of chitosan, based on viscosity determination. The
reported solid to solution ratios range from 1:10 to 1:100 on a wet basis, and 1:4 on a dry basis or
when dry heating is used.
6. Particle Size
Particle size in chitosan productions has sparked controversial reports on its effect on
chitosan quality. Some agree that small particle size is better than large particle size. According
to Bough et al. (1978), smaller particle size (1mm) results in a chitosan product of both higher
viscosity and molecular weight than that of larger particle size (above 2 to 6.4 mm). The larger
particle sizes require longer swelling time resulting in a slower deacetylation rate. However,
Lusena and Rose (1953) indicated that the size of chitin particle within the 20-80 mesh range
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