The gel prepared using Nemipterus virgatus (N. virgatus) surimi alone still has some defects in texture and taste. Complexing with polysaccharides is an efficient strategy to enhance its gel properties. The main objective of this study was to analyze the relationship between the gel quality and molecular interaction of N. virgatus surimi gel after complexing with tapioca starch. The results make clear that the gel strength, hardness, and chewiness of surimi gel were increased by molecular interaction with tapioca starch. At the appropriate addition amount (12%, w/w), the surimi gel had an excellent gel strength (17.48 N), water-holding capacity (WHC) (89.01%), lower cooking loss rate (CLR) (0.95%), and shortened T₂ relaxation time. Microstructure analysis indicated that the addition of tapioca starch facilitated even distribution in the gel network structure, resulting in a significant reduction in cavity diameter, with the minimum diameter reduced to 20.33 μm. In addition, tapioca starch enhanced the hydrogen bonding and hydrophobic interaction in the gel system and promoted the transformation of α-helix to β-sheet (p < 0.05). Correlation analysis showed that the increased physicochemical properties of surimi gel were closely related to the enhanced noncovalent interactions. In conclusion, noncovalent complexation with tapioca starch is an efficient strategy to enhance the quality of surimi gel.

This study delves into the feasibility of developing an intestinal delivery system for curcumin using whey protein as the wall material, employing a simple and eco-friendly (without using organic solvents) pH-induced protein-polyphenol co-assembly strategy. The results indicate that stable complex formed under curcumin concentrations ranging from 0.1 to 0.4 g/L (screened by the preliminary experiment) with particle size between 269 and 287 nm, zeta potential around −38 mV, and curcumin loading capacity ranging from 3.61 to 9.14 mg/g. Curcumin primarily interacts with whey protein through hydrophobic interactions and hydrogen bonds, as confirmed by FT-IR spectroscopy and molecular docking analysis. Curcumin has a different affinity to proteins ranked as bovine serum albumin (BSA) > β-lactoglobulin (β-LG) > α-lactalbumin (α-LA). Curcumin exists in an amorphous state within the protein, which also increases the surface hydrophobicity of the protein (from 565 to 687 AU) and leads to quenching intrinsic fluorescence of the protein. The binding of curcumin causes a transition from random coil to β-sheet in the protein's secondary structure but has a limited impact on its tertiary structure. Stability analysis shows that the complex remains stable in environments with 100–500 mM NaCl and heat treatment at 60–90 °C. In vitro digestion results indicate that the complex aggregates during simulated gastric fluid digestion and decompose during simulated intestinal fluid digestion, effectively enhancing the bioaccessibility of free curcumin by 60 % (P < 0.05). This study provides a theoretical basis for the green processing of protein-based oral delivery systems for lipophilic compounds.

The limited functional properties of tilapia protein isolate (TPI), such as low solubility, emulsification, and foaming, restrict its use in the food industry. However, combining it with hydrophilic proteins can improve these properties. Different assembly methods may affect the structure and functionality of the resulting dual proteins. To study this, tilapia-soybean protein mixtures (T-SPM), complexes (T-SPC), and co-precipitates (T-SPCP) were prepared using physical mixing, pH-regulated complexation, and pH-regulated co-precipitation. The effects of these methods on the structure and functional properties of the tilapia-soybean dual proteins were then analyzed. Structural analysis revealed that TPI combined with SPI through non-covalent forces and disulfide bonds under pH-regulation, leading to structural changes. Compared to T-SPCP, T-SPC showed more hydrophilic groups, with increased free sulfhydryl groups, disulfide bonds, α-helices, and zeta potential, alongside reduced surface hydrophobicity and smaller flake structures. Functional analysis indicated that pH-regulated assembly methods significantly improved the properties of the dual proteins compared to T-SPM. T-SPC exhibited higher solubility, emulsification, and foaming capacity than T-SPCP, which had a more aggregated structure due to pH adjustment to 4.5 during co-precipitation, contributing to its better thermal stability. Thus, T-SPC, assembled by pH-regulation from 12.0 to 7.0, demonstrated superior characteristics. This study offers a theoretical foundation for developing functional dual proteins and their food industry applications.