Effect of protein–polyphenol interactions on the structural and digestive properties of pork myofibrillar proteins

The impact of different doses of protocatechuic acid (PCA), caffeic acid (CFA) and apigenin (AP) on the structural and in vitro digestive characteristics of pork myofibrillar proteins (MP). Results showed that the formation of complexes led to a 9 %–23.5 % increase in turbidity compared with the control group. Spectroscopic analysis revealed that polyphenols caused a static quenching of MP and altered the tertiary structure, which exposed the MP in a hydrophilic environment ( H 0  = 45.91) as shown by a redshift of 14 nm for the MP/CFA sample at high concentration (100 μmol/g). The addition of PCA/CFA/AP promoted the molar ellipticity of CD decrease from −12 mdeg to −16.4 mdeg, indicating that the MP molecular tended to be disordered. Molecular docking and thermodynamic studies confirmed that the formation of the MP/AP complex was mainly through hydrogen bonds, whereas hydrophobic interactions were the primary driving force for MP/PCA and MP/CFA samples. Furthermore, the interaction between polyphenols and MP enhanced the digestive properties of MP as manifested by decreasing the particle size from 851 nm (control) to 594 nm (MP/AP-100), and weakened the high molecular weight bands (170 kDa) observed in SDS-PAGE. The binding of polyphenols to MP at low concentration (20 μmol/g protein) was more conducive to the in vitro gastrointestinal digestion of MP compared to the high dosage.