Structural and rheological properties of kappa (κ)-carrageenans covalently modified with cationic moieties
Cationized kappa-carrageenans containing 2-hydroxy-3-(trimethylammonium)propyl groups with various degrees of substitution (0.13–0.75) were synthesized by reaction of sulfated polysaccharides with 3-chloro-2-hydroxypropyltrimethyl ammonium chloride (QUAB 188) in alkaline solutions through the generation of the corresponding 2,3-epoxy reagent in situ. The structure of the modified algal polysaccharides was characterized without any further treatment or after methanolysis and/or enzymatic depolymerization, by means of spectroscopic tools (FT-IR, NMR, Mass spectrometry) and high-performance size exclusion chromatography (HPSEC). Significant differences in the rheological properties of these cationized kappa-carrageenans have been found depending on the DS values and the presence of KCl salt. Despite their lower molecular weights in comparison with native polysaccharides, cationized kappa-carrageenans with a DS of 0.75 exhibited high viscosity and gelling behaviors mediated by the high density of quaternary ammonium groups.
Keywords(κ)-carrageenan Cationized polysaccharide NMR spectroscopy Chemical and enzymatic depolymerization Rheological behavior
This work benefited from the support of the French Government run by the National Research Agency and with regards to the investment expenditure programme IDEALG ANR-10-BTBR-04. We are greateful to the PRISM core facility (Biogenouest©, UMS, Biosit, Université de Rennes 1- Campus de Villejean- 35043 Rennes cedex, France) for its technical support.
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