Interaction investigation and phase transition of carrageenan/lysozyme complex system

Phase transition of lysozyme/carrageenan (Ly/CRG) complex system with different ratios, pH, ionic strength and temperature conditions was explored through ultraviolet-visible spectrophotometer, fluorescence spectrophotometer, fluorescence microscope, Zeta potential. The results showed that the main force between Ly and CRG is electrostatic interaction, and the Ly/CRG composite system has undergone three phase transition states: co-solubilization, gelation and aggregation. At pH = 1-3, the oppositely charged CRG and Ly form complexes based on electrostatic interaction. Whereas at pH = 12, both CRG and Ly are negatively charged and they repel each other electrostatically. The electrostatic shielding effect of salt ions had a greater impact on the formation of Ly/CRG complex. Temperature had a certain degree of influence on the structure and turbidity of the composite system. The interaction between polysaccharides and proteins can have a significant impact on the structure and stability of complex systems and the study of polysaccharide and protein complexes which will help to expand their application in food and medicine.