Inhibition of the Aggregation of α-Lactalbumin and(-)-Epigallocatechin Gallate in the Presence of Collagen Peptide and the Thermal Stability of the Ternary Complexes Formed

To investigate the effect of fish collagen peptide(CP)on the aggregation behavior of α-lactalbumin(α-La)and epigallocatechin gallate(EGCG),and the thermal stability of the resulting ternary complexby turbidity,dynamic light scattering,fluorescence spectroscopy and circular dichroism four spectroscopy methods. The results showed that,the addition sequence of α-La,EGCG and CP could directly affect the structural properties of the ternary complexes. At 25℃,CP at low concentration could enhance the formation of α-La-EGCG aggregates,with larger particle size,higher PDI and increased turbidity. CP at high concentration could inhibit the formation of α-La-EGCG aggregates,and clear solutions were formed with smaller particle size,lower PDI and decreased turbidity. The zeta potentials showed that,the zeta potentials of these clear solutions were close to 0,which would be related to the mechanism ofthe aggregation of α-La and EGCG by the inhibition of CP. Fluorescent results showed that CP decreased fluorescence emission intensities and caused increase of the polarity around tyrosine residues resulting in a partially unfolded conformation of α-La. Circular dichroism analysis showed that,in the clear solution,CP induced a progressive increase in the proportion of α-helix structure at the cost of the β-sheet and β-turn structures and unordered coil of α-La in α-La-EGCG-CP ternary aggregate. The heated ternary aggregates reduced turbidity and smaller particle size,leading to a more unfolded conformation of α-La. However,heat treatment hardly impacted the ζ-potential of the ternary aggregates and α-La secondary structure.