Inhibition of the interactions of myofibrillar proteins with gallic acid by β-cyclodextrin-metal-organic frameworks improves gel quality under oxidative stress

Abstract

Generally, high levels of natural phenolic antioxidants, which are needed in meat products to exert equivalent antioxidant effects as synthetic antioxidants, can interact with myofibrillar proteins and cause aggregation of the proteins, giving rise to undesirable deterioration of gel quality. In this study, β-cyclodextrin-metal-organic frameworks (K-β-CD-MOFs) were synthesized based on β-CD and K⁺ ions using methanol vapor diffusion method, and used to inhibit excessive covalent and non-covalent interactions between gallic acid (GA) and myofibrillar proteins under oxidative stress without degrading the phenolic antioxidant activity. Results of zeta potential, scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and differential scanning calorimetry (DSC) provided evidence for the formation of GA/K-β-CD-MOFs inclusion complexes. From sulfydryl content, surface hydrophobicity, tryptophan fluorescence, turbidity and particle size analyses, the presence of K-β-CD-MOFs dose-dependently prevented the sulfydryl loss, unfolding of the proteins and formation of insoluble aggregates caused by GA (180 μM/g protein). Dynamic rheology, cooking loss, gel strength, water distribution, microstructure and Raman spectrum were further tested to evaluate effects of K-β-CD-MOFs on the qualities of GA-treated myofibrillar protein gel. Results indicated that more proteins were involved in the formation of a more ordered and homogeneous gel structure with higher gel elasticity and strength, more immobilized water and decreased cooking loss. The overall gel properties of myofibrillar proteins were improved. K-β-CD-MOFs ameliorated the instability of protein structure, manifested as increase in β-sheet content and inter-chain hydrogen bonding and decrease in hydrophobic forces (p < 0.05). This paper provides a novel method to increase the loading amount of phenolic antioxidants without jeopardizing the gel quality of meat products.