Preparation and Properties of Highly Active Dietary Fiber and Carboxymethylcellulose from Gracilaria Residue
|School||Guangdong Ocean University|
|Course||Aquatic Products Processing and Storage Engineering|
|Keywords||Gracilaria Residue Dietary Fiber Preparation Heavy Metal Ions Sodium Carboxymethylcellulose|
With the development of offshore cleaning aquaculture, the three-dimensional ecological farming mode combining the cultivation of fish, shrimp, shellfish with seaweeds will become mainstream. Gracilaria, one of a delicious large seaweeds, is a main seaweed in this ecological farming mode. Gracilaria is mainly used as the raw material extracting agar presently. The gracilaria residue extracted which is rich in dietary fiber is directly abandoned and cause environmental pollution. Extracting dietary fiber from the residue or other utilization of high value can not only prevent environmental pollution, but also make the residue become the valued resource. Full use of the residue will extends the industry chain, that is, ecological aquaculture—gracilaria—agar and increase the environmental and economic benefits of the aquaculture. In this study ,the composition of gracilaria residue were analyzed,the result shows that the residue is rich in dietary fiber. The optimum technology of bleaching dietary fiber with alkaline hydrogen peroxide was found by orthogonal method and the whiteness of dietary fiber can be controlled. The physical and chemical properties were improved by biological method. The optimum methods preparing sodium carboxymethylcellulose from the residue is achieved. The main conclusions are as follows:1. The composition of the residue was analyzed. The result shows that the content of cellulose, hemicelluloses and lignin is respectively 47.21%, 18.5% and 9.9%, while it is excellent material of dietary fiber. The optimum technological conditions for bleaching of dietary fiber with alkaline hydrogen peroxide are pH 8.5, 60℃, 3 h. The relationship between whiteness and the concentration of alkaline hydrogen peroxide can be expressed with equation Y=30.85+8.96*X-1.2*X2（X∈（0,4））, R2=0.9951.2. The swelling capacity, water holding capacity, oil binding capacity and surface structure of the dietary fiber can significantly be improved by activation with cellulase and xylanase. The content of soluble dietary fiber, swelling capacity, water holding capacity and oil binding capacity increase 29%, 15% ,14%, 26%. The swelling capacity, water holding capacity and whiteness are up to 4.71 mL/g , 648% and 48.9% respectively, which exceeded the standard of the western nations（4 mL/g and 400% ）. The study of electron micrograph shows the surface of dietary fiber after activation becomes fluffy and porous, this may be the course of the improvement of its physical properties.3. The residue and its bleaching residue treated with cellulose and xylanase are studied to investigate the adoption of two metals ions Pb2+and Cd2+ in different pH, temperature ,reaction time,initial ions concentration. The result shows that both of them have the highest absorption rate to Cd2+ and Pb2+ at pH 7 , and absorption rate decrease with the increase of concentrations of initial metals ions. The adsorption kinetics and adsorption thermodynamics of both of them to Cd2+ and Pb2+ agree with secondary adsorption model of Lagergren equation and Langmuir adsorption equation. In single metal ions solution, the adsorption rate of both of them to Pb2+ is much stronger than to Cd2+.4. The adsorption dose of the residue and dietary fiber activated with cellulase and xylanase to sodium nitrite was studied, the result shows that the adsorption dose is 91.4 umol/g and 107.7 umol/g, respectively. Under simulating gastrointestinal environment, dietary fiber may hinder Ca2+ and Mg2+ from adsorption. The study from IR spectra shows that main groups for adsorption to sodium nitrite, Ca2+and Mg2+ are hydroxy,carboxyl, sulphur acetate structure and so on.5. The preparation of sodium carboxymethylcellulose （CMC） with the residue was studied by orthogonal method. The result shows that the optimal conditions are as follows: the cellulose was alkalized with NaOH （W/W=3:1）at 25℃for 45 min, chloroacetic acid （ClCH2COOH） was added（W/W=2.5:1）, and the temperature was adjusted to 65℃for 2h. The degree of substitution 0.70 is achieved.