Xiu-Ting He

Adsorption and dilatational rheology of heat-treated soy protein at the oil-water interface: relationship to structural properties.

We evaluated the influence of heat treatment on interfacial properties (adsorption at the oil-water interface and dilatational rheology of interfacial layers) of soy protein isolate. The related structural properties of protein affecting these interfacial behaviors, including protein unfolding and aggregation, surface hydrophobicity, and the state of sulfhydryl group, were also investigated. The structural and interfacial properties of soy protein depended strongly on heating temperature (90 and 120 °C). Heat treatment at 90 °C induced an increase in surface hydrophobicity due to partial unfolding of protein, accompanied by the formation of aggregates linked by disulfide bond, and lower surface pressure at long-term adsorption and similar dynamic interfacial rheology were observed as compared to native protein. Contrastingly, heat treatment at 120 °C led to a higher surface activity of the protein and rapid development of intermolecular interactions in the adsorbed layer, as evidenced by a faster increase of surface pressure and dilatational modulus. The interfacial behaviors of this heated protein may be mainly associated with more flexible conformation and high free sulfhydryl group, even if some exposed hydrophobic groups are involved in the formation of aggregates. These results would be useful to better understand the structure dependence of protein interfacial behaviors and to expand utilization of heat-treated protein in the formulation and production of emulsions.

Soy lipophilic protein nanoparticles as a novel delivery vehicle for conjugated linoleic acid

Soy lipophilic protein nanoparticles (LPP), which present a novel delivery vehicle for conjugated linoleic acid (CLA), were fabricated by ultrasonication of the soy lipophilic protein (LP), which exhibits unique characteristics including a high loading capacity, oxidation protection and a sustained releasing profile in vitro for CLA. The CLA-loaded LPP exhibited a mean diameter of 170 ± 0.63 nm and a loading capacity of 26.3 ± 0.40% (w/w). A coating of sodium caseinate (SC) on the surface improved the colloidal stability of the CLA-loaded LPP. This encapsulation conferred protection against the oxidation of CLA, by which the head space-oxygen consumption and hydrogen peroxide value were obviously decreased in comparison with the SC-encapsulated CLA and CLA alone. The delivery system enables a sustained releasing profile of CLA in a simulated gastrointestinal tract (GIT). These findings illustrate that the LPP could act as an effective delivery device for CLA, which could provide oxidation stability and a sustained release property.

In vitro assessment of the bioaccessibility of fatty acids and tocopherol from soybean oil body emulsions stabilized with ι-carrageenan.

The present investigation aimed to expand the knowledge of the in vitro bioaccessibility of fatty acids and tocopherol from natural soybean oil body emulsions stabilized with different concentrations of ι-carrageenan. Several physicochemical parameters including proteolysis of the interfacial layer, interfacial composition, and microstructure were evaluated with regard to their impact on the bioaccessibility of fatty acids and tocopherol. Results from simulated human digestion in vitro indicated that the bioaccessibility of total fatty acids and tocopherol decreased (62.7-8.3 and 59.7-19.4%, respectively) with the increasing concentration of ι-carrageenan. During the in vitro digestion procedure, ι-carrageenan affected physicochemical properties of the emulsions, thereby controlling the release of fatty acids and tocopherol. These results suggested that soybean oil body emulsions stabilized with ι-carrageenan could provide natural emulsions in foods that were digested at a relatively slow rate, the important physiological consequence of which might be increasing satiety.

Characterization and Interfacial Behavior of Nanoparticles Prepared from Amphiphilic Hydrolysates of β-Conglycinin–Dextran Conjugates

Amphiphilic graft copolymers were prepared from β-conglycinin-dextran conjugates hydrolyzed by trypsin at a degree of hydrolysis (DH) of 2.2%. Nanoparticles were prepared from β-conglycinin, β-conglycinin-dextran conjugates (CDC), and amphiphilic hydrolysates of β-conglycinin-dextran conjugates at DH 2.2% (CDCH) by a desolvation method. All of the nanoparticle samples exhibited spherical structures, as evidenced by dynamic light scattering, transmission electron microscopy, and small-angle X-ray scattering. The nanoparticles prepared from amphiphilic hydrolysates of β-conglycinin-dextran conjugates at DH 2.2% (CDCHN) exhibited higher interfacial pressure and dilatational modulus after long-term absorption at the oil-water interface compared with nanoparticles prepared from β-conglycinin (CN) and β-conglycinin-dextran conjugates (CDCN). This might be mainly associated with the higher surface hydrophobicity of CDCHN, which enhanced adsorption and intermolecular interactions of nanoparticles in the adsorbed layer.