title: Molecular weight distribution, rheological property and structural changes of sodium alginate induced by ultrasound.
abstract: In this study, the effects of ultrasound with different ultrasonic frequencies on the properties of sodium alginate (ALG) were investigated, which were characterized by the means of the multi-angle laser light scattering photometer analysis (GPC-MALLS), rheological analysis, circular dichroism (CD) spectrometer and scanning electron microscope (SEM). It showed that the molecular weight (Mw) and molecular number (Mn) of the untreated ALG was 1.927×105g/mol and 4.852×104g/mol, respectively. The Mwof the ultrasound treated ALG was gradually increased from 3.50×104g/mol to 7.34×104g/mol while the Mnof ALG was increased and then decreased with the increase of the ultrasonic frequency. The maximum value of Mnwas 9.988×104g/mol when the ALG was treated by ultrasound at 40kHz. It indicated that ultrasound could induce ALG degradation and rearrangement. The number of the large molecules and small molecules of ALG was changed by ultrasound. The value of dn/dcsuggested that the ultrasound could enhance the stability of ALG. Furthermore, it was found that ALG treated by ultrasound at 50kHz tended to be closer to a Newtonian behavior, while the untreated and treated ALG solutions exhibited pseudoplastic behaviours. Moreover, CD spectra demonstrated that ultrasound could be used to improve the strength of the gel by changing the ratio of M/G, which showed that the minimum ratio of M/G of ALG treated at 135kHz was 1.34. The gel-forming capacity of ALG was correlated with the content of G-blocks. It suggested that ALG treated by ultrasound at 135kHz was stiffer in the process of forming gels. The morphology results indicated that ultrasound treatment of ALG at 135kHz increased its hydrophobic interaction and interfacial activity. This study is important to explore the effect of ultrasound on ALG in improving the physical properties of ALG as food additives, enzyme and drug carriers.
authors: Beijing Advanced Innovation Center for Food Nutrition & Human Health (BTBU), School of Food & Chemical Engineering, Beijing Engineering and Technology Research Center of Food Additives, Beijing Higher Institution Engineering Research Center of Food Additives and Ingredients, Beijing Key Laboratory of Flavor Chemistry, Beijing Laboratory for Food Quality and Safety, Beijing Technology & Business University, Beijing 100048, China.
authors: Liping
authors: L
authors: Feng
authors: Beijing Advanced Innovation Center for Food Nutrition & Human Health (BTBU), School of Food & Chemical Engineering, Beijing Engineering and Technology Research Center of Food Additives, Beijing Higher Institution Engineering Research Center of Food Additives and Ingredients, Beijing Key Laboratory of Flavor Chemistry, Beijing Laboratory for Food Quality and Safety, Beijing Technology & Business University, Beijing 100048, China. Electronic address: xdxbtbu@126.com.
authors: Yanping
authors: Y
authors: Cao
authors: Beijing Advanced Innovation Center for Food Nutrition & Human Health (BTBU), School of Food & Chemical Engineering, Beijing Engineering and Technology Research Center of Food Additives, Beijing Higher Institution Engineering Research Center of Food Additives and Ingredients, Beijing Key Laboratory of Flavor Chemistry, Beijing Laboratory for Food Quality and Safety, Beijing Technology & Business University, Beijing 100048, China.
authors: Duoxia
authors: D
authors: Xu
authors: Beijing Advanced Innovation Center for Food Nutrition & Human Health (BTBU), School of Food & Chemical Engineering, Beijing Engineering and Technology Research Center of Food Additives, Beijing Higher Institution Engineering Research Center of Food Additives and Ingredients, Beijing Key Laboratory of Flavor Chemistry, Beijing Laboratory for Food Quality and Safety, Beijing Technology & Business University, Beijing 100048, China.
authors: Shaojia
authors: S
authors: Wang
authors: Beijing Advanced Innovation Center for Food Nutrition & Human Health (BTBU), School of Food & Chemical Engineering, Beijing Engineering and Technology Research Center of Food Additives, Beijing Higher Institution Engineering Research Center of Food Additives and Ingredients, Beijing Key Laboratory of Flavor Chemistry, Beijing Laboratory for Food Quality and Safety, Beijing Technology & Business University, Beijing 100048, China.
authors: Jie
authors: J
authors: Zhang
mesh_terms: D000464:Alginates / Q000737:chemistry*; D020723:Glucuronic Acid / Q000737:chemistry; D006603:Hexuronic Acids / Q000737:chemistry; D008970:Molecular Weight; D012212:Rheology; D000069453:Ultrasonic Waves
chemical_list: D000464:Alginates; D006603:Hexuronic Acids; D020723:Glucuronic Acid
keywords: Hydrophobic interaction; Molecular weight distribution; Sodium alginate; Structure; Ultrasound; Viscosity