Surimi wash water treatment by chitosan-alginate complexes

2.4. Chitin and chitosan production
The chitin production methods from crustaceans of Hackman, Whistler &
BeMiller, Horowitz, Reseman & Blumenthal, Foster & Hackman, Takeda & Abe
and Takeda & Katsuura have been extensively reviewed (Muzzarelli, 1973, 1977).
They all begin with size reduction of the raw material and the protein and
carotenoids resulting from this step are used as feed ingredients. Production of
chitin continues with demineralization with dilute acid and deproteinization with
dilute alkali and moderate heating. Deacetylation with concentrated alkali and high
temperature converts chitin into chitosan (Wu and Bough, 1978; Savant, 2001;
Gates, 1991). Wu and Bough (1978) recommends demineralization with 0.5 N HC1
followed by washing and then deproteinization with 1% NaOH at 65°C for 1 h with
constant stirring. Alternatively, the process can begin with deproteinization with 1-
2% NaOH at 60-70°C followed by demineralization (Savant, 2001; Gates, 1991;
Mireles-DeWitt, 1994; Figure 2). After water washes to neutralize the mixture,
dilute aqueous HCI is added and the mixture allowed standing for 2-3 hours to
remove minerals such as calcium carbonate and calcium phosphate. Washing is
then required to neutralize the mixture followed by dewatering (drying). If chitin is
the final product, size reduction might be necessary. If chitosan is desired, chitin is
then deacetylated using 40-50% NaOH to hydrolyze the N-i acetyl-linkage.
Hydrolysis is carried out at high temperature (100-150°C) or at lower temperature
and lower NaOH concentration for longer times. Deacetylation at higher
temperature produces chitosan with higher degree of deacetylation.
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