Interaction of myofibrillar proteins and epigallocatechin gallate in the presence of transglutaminase in solutions.

The rheological behavior, assembly measurements, thermal stability, molecular conformation, and molecular interactions of myofibrillar proteins (MP) modified by transglutaminase (TGase) and epigallocatechin-3-gallate (EGCG) were investigated. Fluorescence and ultraviolet spectra showed that TGase and ECCG quenched the endogenous fluorescence of MP and improved the exposure of chromophoric and hydrophobic groups of MP caused by unraveling the tertiary structure. TGase and EGCG treatment increased the α-helix and β-turn contents and the structure became more ordered. It also increased the thermal stability of MP and the storage modulus of MP gels as reflected in the rheological and thermal properties tests. Meanwhile, changes in SDS-PAGE, FT-IR, and sulfhydryl contents showed that TGase increased the disulfide bond contents, whereas it decreased after EGCG was added, suggesting that EGCG could react with MP via non-covalent and covalent interactions. Assembly measurements illustrated that TGase increased the turbidity and particle size of MP, while TGase and EGCG treatment accelerated MP aggregation and it was associated with the increase in the EGCG concentration, which was further confirmed by SEM and AFM. This work could contribute new insights into the synergistic effect of TGase and EGCG on modifying MP and guide for its application in surimi processing.