The combination of polyphenols and protein can improve the functional characteristics of protein. How to effectively promote the binding of polyphenols to protein is still a difficult topic. In this study, hydrodynamic cavitation (HC) was used to induce the fabrication of complexes between soy protein isolate (SPI) and different polyphenols (tannic acid (TA), chlorogenic acid (CGA), ferulic acid (FA), caffeic acid (CA), and gallic acid (GA)). The effect of HC on the interaction between polyphenols and SPI was investigated, and the structural and functional properties of the formed complexes were characterized. The results showed that HC treatment led to SPI structure stretching, which increased the binding level of polyphenols, especially that of TA (increased from 35.08 ± 0.73% to 66.42 ± 1.35%). The increase in ultraviolet-visible absorption intensity and quenching of fluorescence intensity confirmed that HC enhanced the interaction between polyphenols and protein. HC treatment reduced the contents of free sulfhydryl and amino groups in SPI-polyphenol complexes and altered their Fourier transform infrared spectroscopy, indicating that HC treatment promoted the formation of C-N and C-S bonds between SPI and polyphenols. Circular dichroism spectroscopy indicated that HC treatment altered the secondary structure of SPI-polyphenol complexes, inducing an increase in α-helix and random coil contents and a decrease in β-sheet content. Regarding functional properties, HC treatment improved the emulsification and antioxidant activity of SPI-polyphenol complexes. Therefore, HC is an effective technique for promoting the binding of polyphenols to protein.

In this study, hydrodynamic cavitation technology was utilized to prepare conjugates of soy protein isolate (SPI) with polyphenols, including resveratrol (RA) and polydatin (PD) from the stilbene category, as well as arctiin (AC) and magnolol (MN) from the lignan category. To investigate the effects of hydrodynamic cavitation treatment on the interactions between SPI and these polyphenols, the polyphenol binding capacity with SPI was measured and the changes in the exposed sulfhydryl and free amino contents were analyzed. Various methods, including ultraviolet–visible spectroscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy, and circular dichroism spectroscopy, were also used to characterize the structural properties of the SPI–polyphenol conjugates. The results showed that compared to untreated SPI, SPI treated with hydrodynamic cavitation exposed more active groups, facilitating a greater binding capacity with the polyphenols. After the hydrodynamic cavitation treatment, the ultraviolet–visible absorption of the SPI–polyphenol conjugates increased while the fluorescence intensity decreased. Additionally, the content of exposed sulfhydryl and free amino groups declined, and changes in the secondary structure were observed, characterized by an increase in the α-helix and random coil content accompanied by a decrease in the β-sheet and β-turn content. Furthermore, the SPI–polyphenol conjugates treated with hydrodynamic cavitation demonstrated improved emulsifying characteristics and antioxidant activity. As a result, hydrodynamic cavitation could be identified as an innovative technique for the preparation of protein–phenolic conjugates.

Effects of different ionic strengths (0.2, 0.4, and 0.6 mol/L) and different hydrodynamic cavitation (HC) treatment times (0, 1, 2, 3, and 4 min) on the conformation and gel properties of tilapia myofibrillar proteins (TMP) were investigated. The results showed that the solubility of TMP was significantly enhanced (p < 0.05) with the increase in NaCl concentration, and the gel characteristics were significantly improved. After HC treatment of TMP, the average particle size was significantly reduced (p < 0.05) and solubility was significantly enhanced (p < 0.05) with the increase in treatment time, the internal hydrophobic groups and reactive sulfhydryl groups were exposed. The intrinsic fluorescence spectra showed the unfolding of the spatial tertiary structure of proteins, and the circular dichroism spectroscopy showed the significant reduction in the content of α-helix in the secondary structure of the proteins (p < 0.05). In addition, the WHC and gel strength of the TMP heat-induced gels were enhanced, which improved the microstructure of the gels, and scanning electron microscopy showed that the gel network of the TMP gels became denser and more homogeneous. Dynamic rheology results showed that HC treatment resulted in a significant increase in the final G’ and G” values of TMP. In conclusion, HC treatment was able to improve the physicochemical structure and gel properties of TMP at different ionic strengths. This study presents a novel processing technique for the quality maintenance aspect of salt-reduced surimi gel products.