Fibrillation of soy protein isolate in the presence of metal ions: Structure and gelation behavior.

The structure and functional properties of protein fibrils are closely related to environmental factors in fibrillation. Herein, soy protein isolate fibrils (SPIFs, 22 mg/mL) were prepared under acid-heating conditions in the presence of 100 mM metal ions (K+, Na+, Ca2+, Mg2+, and Fe3+). Except for Fe3+, fibrillation and subsequent larger fibril aggregates were promoted, ultimately leading to gel formation. Compared with K+ or Na+, the addition of Ca2+ or Mg2+ resulted in more organized SPIF structures with increased ß-sheet contents and higher ThT fluorescence intensities. Furthermore, both of them resulted in longer fibrils with an average contour length of 700-800 nm, which significantly enhanced the storage modulus. However, the presence of Fe3+ accelerated protein hydrolysis and inhibited SPIF formation, resulting in samples consistently exhibited liquid behavior. These findings provide a foundation for understanding the influence of metal ions on regulating the fibrillation and gelling properties of SPIFs.

Application of soy protein isolate fiber and soy soluble polysaccharide non-covalent complex: A potential way for pH-triggered release.

The non-covalent interactions between protein and polysaccharide have the potential to design responsive materials. In this study, soy protein isolate fiber/soy soluble polysaccharide (SPIF/SSPS) non-covalent complex was used to create an emulsion, and the pH-response performance was evaluated by investigating their microstructure, interfacial properties, and stability at pH values of 2.0-10.0. The SPIF/SSPS complex was relatively stable at pH 2.0 and 4.0, and the corresponding emulsions had uniform droplets that showed outstanding storage stability after 21 days. However, the SPIF/SSPS complex was dissociated gradually with the elevation of pH, especially under alkaline condition, that caused the flocculation and coalescence in emulsion. This phenomenon not only relate to electrostatic repulsion, but also relate to the disintegration of SPIF. Furthermore, the encapsulated curcumin is released rapidly from emulsion when the pH increased above 6.0. This research may provide an outstanding pH-response strategy that have the potential for pH-triggered release.

Tunable arrangement of hydrogel and cyclodextrin-based metal organic frameworks suitable for drug encapsulation and release.

The present study focused on the integration of beta-cyclodextrin based metal-organic frameworks (ß-CDMOF) with polymer to obtain hybrid materials with advantageous properties compared to traditional single-component polymers or metal-organic frameworks (MOF) matrixes. We fabricated two complexes with different morphology and structure. During the in situ growth of ß-CDMOF around the hydrogel, potassium ions on polysaccharides gradually dissociated to participate in the growth of crystals, while other potassium ions on the carboxylic acid groups provided bridges between crystals and hydrogel, forming a necklace-shaped complex (SHPs@ß-CDMOF). Hydrogen bonding and coordination interactions between ß-CDMOF and hydrogel are present in a dendritic sandwich-shaped complex (ß-CDMOF@SHPs). Furthermore, using the hydrophobic molecule curcumin as a model drug, we have demonstrated that SHPs@ß-CDMOF and ß-CDMOF@SHPs hybrid materials stabilize the included drug and have potential for controlled drug release. Collectively, the integration of MOF with polymer holds a great promise for drug delivery applications.

Fabrication and emulsifying properties of non-covalent complexes between soy protein isolate fibrils and soy soluble polysaccharides.

Non-covalent complexes (SPIF/SSPS) of soy protein isolate fibrils (SPIF) and soy soluble polysaccharides (SSPS) were fabricated and used to stabilize oil-in-water (O/W) emulsions. FT-IR spectroscopy and zeta potential results demonstrated that the interactions between SPIF and SSPS mainly include hydrogen bonding and electrostatic interactions. The presence of SSPS decreased the particle size and surface hydrophobicity of SPIF, resulting in a decrease and redshift of the fluorescence intensity. During the interfacial adsorption process, SPIF/SSPS complexes had lower diffusion and penetration rates compared with pure SPIF because of their hydrophilic region, but the molecular reorganization rate increased. Emulsions stabilized with the SPIF/SSPS complex at 5 : 5 (i.e., 1 : 1) ratio had both an excellent emulsifying activity index (EAI) of 26.17 m2 g-1 and an excellent emulsifying stability index (ESI) of 93.01%, as well as the smallest emulsion droplet particle size of 1.74 µm. Meanwhile, no flocculation was observed in this emulsion which is attributed to the sufficient steric stabilization provided by the hydrophilic SSPS. After three weeks of storage, there was no phase separation observed in the emulsions stabilized by SPIF/SSPS complexes in 5 : 4 and 5 : 5 ratios and the Turbiscan stability indices were 17.86 and 15.14, respectively, much lower than the other emulsion formulations tested.

Contribution of soybean polysaccharides in digestion of oil-in-water emulsion-based delivery system in an in vitro gastric environment.

This study aims to evaluate the effects of soy soluble polysaccharide and soy hull polysaccharide on stability and characteristics of emulsions stabilised by soy protein isolate in an in vitro gastric environment. Zeta potential and particle size were used to investigate the changes of physico-chemical and stability in the three emulsions during in vitro gastric digestion, following the order: soy protein isolate-stability emulsion < soy protein isolate-soy soluble polysaccharide -stability emulsion < soy protein isolate-soy hull polysaccharide-stability emulsion, confirming that coalescence in the soy protein isolate-stability emulsion occurred during in vitro gastric digestion. Optical microscopy and stability measurement (backscattering) also validate that addition of polysaccharide (soy soluble polysaccharide and soy hull polysaccharide) can reduce the effect of simulated gastric fluid (i.e., pH, ionic strength and pepsin) on emulsion stability, especially, soy protein isolate-soy hull polysaccharide-stability emulsion, compared with soy protein isolate-stability emulsion. This suggests that the flocculation behaviours of these emulsions in the stomach lead to a difference in the quantity of oil and the size and structure of the oil droplets, which play a significant role in emulsion digestion in the gastrointestinal tract. This work may indicate a potential application of soy hull polysaccharide for the construction of emulsion food delivery systems.

The production of gel beads of soybean hull polysaccharides loaded with soy isoflavone and their pH-dependent release.

Core-shell hydrogel beads were successfully produced from soybean hull polysaccharides (SHP). Using electron microscopy, the beads were found to be spherical with smooth surfaces and have tight gel network internal structures. Fourier transform infrared spectroscopy, differential scanning calorimetry, and X-ray diffraction were used to investigate the interaction between soy isoflavone and SHP in the gel beads mesh-like structure. Furthermore, the encapsulation efficiency and loading capacity of gel beads for soy isoflavone are 66.90% and 4.67%, respectively, and have the ability of pH-responsive release in vitro. Through the mathematical model of kinetics, we found that the release of soy isoflavone from gel beads showed Fickian diffusion in release media (pH 2.0 and 7.4), but showed non-Fickian diffusion at pH 4.0 and 6.8. This polymer can be extended to prepare more versatile delivery and controlled release system, appealing for food, pharmaceutical, biomedicine and cosmetics applications.