Effect of β-cyclodextrin on whey protein-epigallocatechin gallate interaction

This study aimed to explore the influence of whey protein–epigallocatechin gallate interaction. Nonreducing cyclic polysaccharide (β-cyclodextrin, i.e., β-CD) was added to epigallocatechin gallate (EGCG) and whey protein (WP) to regulate the interaction between polyphenols and proteins. Based on the transmittance, oxidation resistance, and spectral analysis, we used differential scanning calorimetry, Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM) to characterize the effects of β-CD on the interaction between polyphenols and proteins. The light transmittance of WP was 74.61%, and the EGCG addition reduced the light transmittance of WP by 2.8%. The maximum absorption peak of WP was around 280 nm. EGCG enhanced the fluorescence intensity of WP, caused the blue shift, and also reduced the fluorescence intensity of WP. In addition, the interaction between WP and EGCG also weakened the antioxidant activity of EGCG. β-CD could improve the light transmission and oxidation resistance of the EGCG-WP hybrid system to a certain extent. The β-CD addition had little effect on the thermal stability of the mixed system. In WP–EGCG and β-CD–WP–EGCG systems, the peak intensity of absorption peaks in each group was different. The EGCG addition reduced the crystallinity of the mixed system by 6.25%, and β-CD alleviated this phenomenon to a certain extent. The formed complex became relatively chaotic by adding WP and EGCG, and the system became tightly connected and ordered with the interaction of 0.03% β-CD with WP–EGCG. This study provided the basis for the interaction between β-CD, WP, and EGCG.