LAUSR

Abstract Lysozyme (LYS) and κ-carrageenan (κ-CRG) are important components widely used in food and pharmaceutical products. In this work, we investigated the interactions in the aqueous mixtures of LYS and κ-CRG and the structural transformation of the LYS/κ-CRG complexes. When co-soluble polymers and soluble complexes are formed in near-neutral environment, insoluble complex coacervates are formed at lower pHs. Significant accumulation and size expansion of coacervate particles occur at pH = 4.0 where maximum interactions are presented at the mixing ratio of LYS/κ-CRG = 2:1. The coacervate system is flexible to rearrange to reach a charge balanced state by gradual protonation of LYS and κ-CRG. Addition of NaCl up to 50 mM weakens the electrostatic attractions among the aggregates through counterion binding. Thermal stability of LYS by forming complex coacervates differs from that in water, and effective protection of protein is achieved as the unfolding temperature is increased by 9 °C.