| Oatβ-glucan（OBG）is a kind of natural viscous polysaccharide,which mainly exists in the endosperm layer and aleurone layer cell wall of oat granules.It has various health effects such as lowering blood pressure,lowering blood lipid and preventing cardiovascular diseases.The United States Food and Drug Administration,the United Nations Health Statement and other authorities and professional associations have issued OBG health statements.OBG not only has a wide consumer market,but also has rich raw materials.Further research on OBG is conducive to promoting its application in many fields and increasing the added value of oat.In this paper,oatβ-glucan was extracted from Zhangjiakou Oat,and its structure was characterized,the properties of solution were determined,the gel mechanism was explored and the application of emulsion was studied.The main research results are as follows:Firstly,two OBGs with different molecular weights were extracted and isolated.The weight average molecular weight was 80.73×104g/mol and 8.05×104g/mol,the yield was4.86%and 3.32%,and the purity was 94.21%and 90.43%,respectively.Subsequently,the structures of the twoβ-glucans were compared and analyzed.The results of monosaccharide composition analysis showed that glucose was the only monosaccharide in the molecular structure of both polysaccharides.After the specificβ-（1,3）-（1,4）-glucanase hydrolysis,the main monomer structure of the two OBG with different molecular weights were both fiber-triosaccharide（DP3）and fiber-tetrasaccharide（DP4）,and the results of NMR showed that the ratio of fiber-triosaccharide to fiber-tetrasaccharide was 1.4.The ratio of beta-（1,4）-glucoside bond to beta-（1,3）-glucoside bond was 2.3.In the infrared spectrum,the strong absorption near 1021 cm-1is due to the stretching vibration of C-O-C bonds in the sugar chains of different units ofβ-（1,3）-glucose residues andβ-（1,4）-glucose residues in OBG,and the absorption peak at 895 cm-1is the absorption peak with typicalβ-glucoside bonds.Compared with OBG-2,the oligosaccharide fragments with polymerization degree greater than 4 generated by the hydrolysis of OBG-1 were significantly more,and the two molecular weight OBGs showed a fibrous structure.However,the surface of the large molecular weight OBG-1 was smooth,dense and without fine pores,while the surface of the small molecular weight OBG-2 was rough and porous.In addition,the X-ray diffraction results show that there are crystal and amorphous structures in the structure of OBG-1,while the dispersion peaks of OBG-2 are amorphous.Secondly,by comparing the rheological properties of OBG with two molecular weights,the conformation of OBG in aqueous solution was investigated.In a certain concentration range,the two molecular weights of OBG showed typical pseudoplastic fluid properties,namely shear thinning phenomenon.The apparent viscosity analysis showed that the viscosity ofβ-glucan of the two molecular weights increased exponentially with the increase of polysaccharide concentration when the concentration of OBG-1 was more than 8%and that of OBG-2 was more than 24%,indicating that OBG-1 showed higher viscosity in aqueous solution.The molecular weight of OBG-1 was homogenized by ultrasonic method.The conformation of OBG polysaccharide chain in aqueous solution was simulated by dynamic/static light scattering and viscosity measurement.The relationship between Rgand Mwis determined as[η]=0.24Mw0.55and Rg=48Mw0.76.Combined with the conformation parameterρ,OBG showed a linear compliant chain conformation in aqueous solution.The chain length of OBG was 200-300 nm,the chain width was 5-15 nm,and the chain height was0-4.5 nm.Then,according to the rheological properties,it is found that under certain conditions,both OBG-1 and OBG-2 can form gel structure,so the gel mechanism of OBG is explored.The gel eutectic point of OBG-1 is 8%,and it can be seen from the apparent structure of the gel that OBG-1 forms a compact gel structure at a concentration of 12%.However,the gel eutectic point of OBG-2 is 24%and an apparent compact gel is formed at a concentration of30%.DSC results show that the enthalpy of OBG-1 gel is 3.84 J/g,while that of OB-2 gel is4.98 J/g.In addition,when the concentration of OBG-1 is 10%and the concentration of OBG-2 is 30%,the typical gel characteristics formed by them are that the ratio of the energy storage modulus（G’）and the loss modulus（G"）is greater than 1.By studying the effects of molecular weight,sodium chloride,p H,urea,boric acid and dimethyl sulfoxide on the texture properties of OBG gel,it is concluded that hydrogen bond and electrostatic interaction play main roles in the formation of OBG gel.Finally,the conditions of OBG stabilized emulsion were optimized.The results showed that when the molecular weight of OBG was 4.04×104 g/mo L,the concentration of polysaccharide was 1%,the oil phase was 0.5%,and the p H of water phase was 8.3,the homogeneous nanoemulsion with particle size of 418 nm and emulsion stability was 100%could be prepared.After 15 days of storage,it could also maintain good stability（97%）. |
