Effect of deproteination and deacetylation conditions on viscosity of chitin and chitosan extracted from Crangon crangon shrimp waste

Abstract

Deproteination of decalcified chitin from Crangon crangon shells and deacetylation to chitosan was investigated to find out optimum conditions for a high viscosity chitosan. Deproteination was carried out with an optimum shrimp shell:alkali (s:a) ratio of 1:4 from 30 °C to 65 °C and at each temperature, incubation times were varied from 2 to 5 h for maximal efficiency. Viscosity of the chemically extracted chitin samples at different temperature–time conditions ranged from 195 to 391 mPa s. A two-way ANOVA with Bonferroni post test was performed on experimental data. Chitin extracted at various temperatures and incubation times was deacetylated with 50% (w/w) NaOH at increasing reaction times. The highest chitosan viscosity of 1976 mPa s was observed in a sample deproteinated for 5 h at 55 °C and deacetylated for 1 h at 105 °C and 2 bar N 2 pressure. One-way ANOVA test for chitosan viscosity measurements indicated a significant P value of <0.05. Viscosity was not dependent on acetic acid release during deacetylation. A central composite design (CCD)–response surface analysis (RSA) was carried out and the resulting optimised model solutions confirmed the results. Highly viscous chitin and chitosan compared to commercially available products could be prepared within a short time by selecting suitable process conditions.