Studies on the effects of preheated β-lactoglobulin on the physicochemical properties of theaflavin-3,3′-digallate and the interaction mechanism

Teaflavin-3,3 '-digallate (TFDG) is a sensory and health benefit substance in tea beverage, but is usually eliminated during processing due to the formation of tea cream by binding with proteins. In order to retain the TFDG, beta-lactoglobulin (beta-LG) was used to bind with TFDG and avoid the formation of tea cream. The results of physicochemical tests and entropy weight-TOPSIS showed that the best beta-LG-TFDG dispersion (TFDG concentration: 0.468 g/L) had low particle size (37.29 nm), high electrical potential (-32.43 mv), high transmittance (88.52%), and strong antioxidant activity (84.82%), when the preheated temperature of beta-LG was 85 degrees C and the molar ratio was 1:2. The multispectral experiment results showed that TFDG interacted with beta-LG via static quenching, and preheated treatment of beta-LG enhanced the interaction between beta-LG and TFDG. CD spectroscopy suggested that TFDG induced slight changes in the secondary structure of beta-LG. The results of molecular dynamics showed that preheated treatment leading in the changes in tertiary structure of beta-LG, opening of key ring region of beta-LG and exposing the active cavities of beta-LG, which enhances the intermolecular forces between TFDG and beta-LG. What's more, molecular docking was proved that preheated treatment of beta-LG enhances the hydrophobic interactions and hydrogen bonds, which dominated the interaction between TFDG and beta-LG. The results proposed in this research could further reducing tea cream formation and improving the healthy and sensory performances of tea beverage by using preheated beta-LG without preserving both the tea pigments and the active nutrients.