Preparation and Quality Identification of Chitosan and Chitooligosaccharide from Antarctic Krill

In this study, Antarctic krill shell was used as raw materials to prepare chitosan and chitooligosaccharide, their quality were also identified. After demineralization and deproteinization of Antarctic krill shell, deacetylation reaction conditions (alkali concentration, reaction temperature and reaction time) were explored to prepare Antarctic krill chitosan with high degree of deacetylation, and the physicochemical properties of chitosan were identified. The enzymatic hydrolysis conditions (chitosanase dosage and hydrolysis time) were explored to prepare high purity chitooligosaccharide, and the structural characteristics were identified. Results showed that Antarctic krill chitosan was finally prepared by 60% of sodium hydroxide deacetylation at 110 ℃ for 4 h, the deacetylation degree was 85.74%, the viscosity average molecular weight was 305.65 kDa, moisture content was 4.66%, ash content was 0.98% and acid insoluble content was 0.40%. The physicochemical properties of Antarctic krill chitosan met the food grade quality. Chitooligosaccharide was prepared by 0.2% (m/V) of chitosanase hydrolysis for 16 h. The yield of chitooligosaccharides from Antarctic krill chitosan was 46.0%. IR and NMR spectra showed all the characteristic signals of chitooligosaccharide. The MS results showed that chitooligosaccharide was mainly composed of disaccharide (GlcN)₂, trisaccharide (GlcN)₂-GlcNAc and tetrasaccharide (GlcN)₃-GlcNAc. In this study, the preparation of high quality chitosan and chitooligosaccharide provided technical support for the comprehensive utilization of Antarctic krill shells and the development of Antarctic krill new products.