The Preparation And Rheological Properties Of G. Lamaneiformis Agar Polysaccharide

Agar is a complex water-soluble polysaccharide extracted from red algae, which is composed of agarose and agaropectin, used widely in food, biological technology and other domains. Agaropectin has not attracted attention as a waste in the extraction of agarose. Agar polysaccharide are used as the research object in this thesis. The main results are as follows:(1) Study on the extraction methods of agarose: The color, transparency, ash, sulfate radical, galactose and gel strength of agarose were use to confirm the processing condition of acid, alkali and alcohol by orthogonal experiment. The results showed the optimum processing condition was that crude agarose was soaked in the 8% NaOH at 80℃for 2h and washed until neutral, then soaked in 0.1mol/L HCl for 20min and neutral again, then soaked in 60% alcohol for 8h, washed till no alcohol left, then pure agarose was got after freeze-drying.(2)The technical indexes of purified agarose were compared with the BBI standard agarose's. The results showed that the color, transparency, ash, sulfate radical, galactose and gel strength of purified agarose could come up to the standard and even better than the BBI standard samples. And the purified agaroes had a good ability on gentian violet electrophoresis and agarose gel electrophoresis of dna,which could meet the requirements of gel electrophoresis in the advanced biochemistry.(3)The ability of eliminating free radical of agaropectin oligosaccharide was studied .The results showed that the agaropectin oligosaccharide could eliminat free radical in water phase, and the IC50 against·OH free radical and O2˙- were 0.03 mg/ml and 0.6mg/ml respectively, which was better than agar oligosaccharide.(4) Rheological properties and gelation properties of agar were investigated. The gelling point, melting point and the gel strength of agar were detected with MCR101 rheometer and TA texture testing instrument. Rheological properties of agar were affected by its concentration , temperature and the addition of salt ( such as NaCl , CaCl2) and sucrose. Apparent viscosity exhibited shear thinning behavior following the power law model. Apparent viscosity increased with the increase of concentration, and decreased with the increase of temperature. The decrease in viscosity followed an Arrhenius temperature dependence. Agar solutions exhibited typical"weak gel"properties by small strain oscillatory measurements. The results indicated that agar solution was characterized as a gel properties , and which could form a kind of heat reversible gel . The gelling point of agar was lower than its melting point. The gel strength of agar could be affected by its gel time, and the addition of salt (such as NaCl, CaCl2) and sucrose.(5) The synergy of agar and sophora bean gum was studied. The results showed that the agar could form gel while the sophora bean gum couldn't. However gel could be formed when mixed the agar and sophora bean gum.The viscosity, thixotropy, gel strength and water-holding ability of agar solution were enhanced significantly, which indicted there was synergistic effect between agar and sophora bean gum, and the best blending ratio of agar/sophora bean gum was 8/2.