How Heat Treatments Affect EGCG-Casein Complexes

In this study, researchers looked into how different heating methods in the dairy industry affect the structure and function of epigallocatechin-3-gallate-casein (EGCG-CS) complexes. They heated these complexes at various temperatures – 65°C for 30 minutes, 72°C for 15 seconds, 85°C for 15 seconds, 100°C for 5 minutes, and 121°C for 5 seconds. They used a tool called Fourier transform infrared spectroscopy (FT-IR) and found that the heat caused changes in the complex's structure, especially in the protein part called amide I.Scientists also used field emission scanning electron microscopy (FESEM) and viscosity measurements to see what happened. They found that treatments above 85°C broke non-covalent bonds, making the complex unstable and less viscous. Interestingly, when they looked at surface hydrophobicity, solubility, and sulfhydryl group content, they saw a pattern: these properties first increased and then decreased with higher temperatures. This was because the casein protein became stretched and exposed more hydrophobic parts. A surprising find was that heating at 85°C for 15 seconds actually improved the structural stability and capabilities like foaming and emulsifying. This could be useful for industrial applications.