Preparation, characterization, and modification mechanism of agar treated with hydrogen peroxide at different temperatures

Agar was dispersed fully in ethanol solution with certain mass fraction, and a series of modified agar were prepared with hydrogen peroxide treatment at different temperatures. Results indicated that the agars can be desulfated, oxidized and degraded by hydrogen peroxide. The modified agars exhibited lower sulfate content and ash content than raw agar because hydrogen peroxide had a good removing effect on alkali-stable sulfate. As the reaction temperature increased, the carbonyl content of modified agar increased which means raw agar can be oxidized by hydrogen peroxide. The molecule-chain breakage and molecular-weight reduction indicated that the agars can be degraded after hydrogen peroxide treatment. FT-IR spectrum of modified agars at 1156 and 1071 cm(-1) showed differences confirmed that the structure of modified agars had changed. Thermogravimetric analysis revealed that the modified agars had higher thermal stability than raw agar. Compared with raw agar, the modified agars showed novel physical properties including high gel strength, low viscosity and low ash content. All physicochemical properties changes were more conducive to the application of agar, which means the modified agar had better quality and wider application value than raw agar.