Study On The Structure Of The Complex Of Carrageenan And Alkaline Protein

Polysaccharides and proteins are important components in food,and the submicrostructure formed by their self-assembly behavior can improve the physical and chemical properties of food systems such as interface properties,thermal stability,and rheological properties.Since the isoelectric point of most food proteins is lower than7.0,the research on the interaction between acidic proteins and polysaccharides started early,the research methods are more mature,and the rules and results are relatively clear.The law of the interaction between alkaline protein and polysaccharide and its application and promotion still need to be supplemented and improved.This paper tries to use carrageenan with different charge densities and alkaline proteins(lysozyme)or peptides(?-polylysine)as models,by changing the interaction strength and other parameters,such as adjusting the compound ratio,system pH and ion concentration,constructing soluble complexes with different structural characteristics and complex aggregation.The multiphase system is used to explore the influence of the charge density of polysaccharides on the phase behavior of the polysaccharide/protein electrostatic complexes,in order to provide new ideas for the development of new structure foods and the solution of key problems.The specific research conclusions of this paper are as follows:(1)The linear charge density,pH and salt ion concentration of polysaccharides have significant effects on the electrostatic interaction of the ?-polylysine/carrageenan composite system.After the alkaline peptide(?-polylysine)is compounded with carrageenan,the three systems all become insoluble aggregates.When the pH is lower than the protein p I,the difference between the turbidity of the complex solution and the microstructure of the complex aggregate is not obvious.Under the same conditions,the stronger charge density of carrageenan binds to ?-polylysine more tightly and is less affected by changes in pH and salt concentration.The interactions of the three groups of complex systems all appear to be promoted at the low salt concentrations and inhibited at high salt concentrations.(2)Carrageenan with different charge densities(?-carrageenan > ?-carrageenan >kappa selenocarrageenan)are compounded with lysozyme to study the effects of polysaccharide charge density,pH and salt ion strength on the interaction of lysozyme/carrageenan.Under the same conditions,all the three groups of composite systems produced insoluble complex aggregates.The structure of complex aggregates formed by compounding carrageenan with stronger charge density andlysozyme is more stable and is less affected by changes in pH and salt ion concentration which is similar to the conclusion drawn in the first chapter.(3)After the ?-carrageenan and ?-carrageenan with high charge density and high viscosity interact with alkaline protein,they can encapsulate the protein,forming a three-microgel network structure with strong stability,and improve the thermal stability of the protein and increase its thermal denaturation temperature.?-selenocarrageenan has a low charge density,and the denaturation temperature of its complex aggregates is lower than the denaturation temperature of protein monomers.It is speculated that the linear charge density difference with polysaccharides is related to the molecular conformation.