Preparation and Physicochemical Properties of Glutaric Acid Esterified κ-Carrageenan

The effects of the concentration of glutaric anhydride, pH value, reaction temperature, carrageenan concentration and reaction time on the degree of substitution (DS) of the product in the preparation of glutaric acid esterified carrageenan (GC) with κ-carrageenan as raw material and glutaric anhydride as esterification agent were studied. The technological conditions for the preparation of GC were obtained as follows: glutaric anhydride concentration 4%, pH value 8～8.5, reaction temperature 30 ℃, carrageenan concentration 7.50%, reaction time 2 h, DS 0.077. The products were characterized by IR, whiteness, viscosity, scanning electron microscopy and thermogravimetry. The results showed that: the absorption characteristic peaks of ester carbonyl and carboxyl groups appeared in curve of GC at 1734 cm⁻¹ and 1576 cm⁻¹, and the peaks increased with the increase of DS. Compared with the original carrageenan, the whiteness of esterified carrageenan powder increased slightly, the surface of the particles becomed rough, and there were some depressions and holes in the surface layer, but the effect of thermal stability is not obvious; the viscosity of the esterified carrageenan solution decreased, but the emulsifying property and emulsifying stability were improved significantly. Taken together, after esterification with glutaric anhydride, the structure and properties of κ-carrageenan are changed and the application range of κ-carrageenan is widened.