Structural and rheological properties of xanthan gum/lysozyme system induced by in situ acidification

Structural and rheological properties of xanthan gum/lysozyme (XG/Ly) system induced by electrostatic interaction through in situ acidification were investigated. The two biopolymers transited from co-solubility state to form soluble complexes, and finally produced tenuous network as the pH further decreased. The fluorescent images indicated that the network was cross-linked of XG chains by Ly, liking a polymerization process which resulted in the sol-gel transition by electrostatic interactions. High Ly content could accelerate the phase transition at the same pH condition, while XG played a contrary role. XG addition could enhance the thermal stability of Ly. The phase transition was also illustrated by ζ-potential at different pHs. The boundary parameters were determined to distinguish the phase transition regions. At the pH higher than pH_φ, the negatively liked XG and Ly were in co-soluble state. They formed soluble complexes at the pH between pH_φ and pH_g, and gel was obtained with net microstructure as the pH continuously decreased (lower than pH_g). The paper provides practical parameters that may be applicable in controlling the structure, texture, and stability of polysaccharide/protein system, as well as in food and medicinal application with various purposes.