Jian-Hua Zhu

Formation of soy protein isolate-dextran conjugates by moderate Maillard reaction in macromolecular crowding conditions.

BACKGROUND Several methods have been reported for the conjugation of proteins with polysaccharides. Protein-polysaccharide conjugates can be formed by traditional dry heating, but this process is not attractive from an industrial viewpoint, and no commercial conjugates have been manufactured in this way. In the present study, in order to develop a more practical reaction method, macromolecular crowding was used to attach polysaccharides to proteins. RESULTS Soy protein isolate-dextran conjugates (SDCs) were prepared via the initial stage of the Maillard reaction in macromolecular crowding conditions. The impact of various processing conditions on the formation of SDCs was investigated. The optimal conditions chosen from the experiments were a soy protein isolate/dextran ratio of 1:1 (w/w), a pH of 6.5, a reaction temperature of 60 °C and a reaction time of 30 h. Circular dichroism spectroscopy showed that the secondary and tertiary structures of the conjugates were changed significantly. Structural flexibility increased, allowing better display of their functional characteristics. The conjugates had a composition with various sizes, especially macromolecules, according to gel permeation chromatography. Thermal analysis showed that the thermal stability of the conjugates was improved. CONCLUSION The production of SDCs under macromolecular crowding conditions appears to be an effective and promising technique, representing an advance over classic protein glycosylation methods.

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.

Rheological Properties of Soybean β-Conglycinin in Aqueous Dispersions: Effects of Concentration, Ionic Strength and Thermal Treatment

Steady shear and dynamic oscillatory measurements were used to investigate the effect of concentration, ionic strength and thermal treatment on rheological properties of soybean β-conglycinin in aqueous dispersions. SDS-PAGE and Differential Scanning Calorimetry (DSC) showed that β-conglycinin exhibited partial denaturation and formation of aggregates during isolation. Under steady shear flow, strong shear-thinning behavior was observed with increasing shear rate from 0.001 to 1200 s−1. A dispersion of β-conglycinin (≥5% w/v, without applying thermal treatment) exhibited gel-like dynamic mechanical spectra at 20°C. This suggested that β-conglycinin in aqueous dispersions showed rheological properties of typical weak gel-like (entanglement) or semi diluted polymeric solution. Weak gel network of β-conglycinin was susceptible to ionic strength, suggesting that electrostatic forces play an important role in the formation of weak gel network. These properties of β-conglycinin have practical significance for the food processors in the formulation of new products.

Fractionation and characterization of soy β-conglycinin-dextran conjugates via macromolecular crowding environment and dry heating.

Conjugates of β-conglycinin and dextran were prepared by heating in solution under macromolecular crowding environment and dry-heating methods, and then fractionated by solubility at pH 4.8 and pH 6.5 and characterized. The results showed that the degree of glycation of the conjugates extracted from pH 4.8 were higher than the conjugates extracted from pH 6.5. Corresponding to the higher degree of glycation, it was supposed that the β-conglycinin of groups 4.8 of macromolecular crowding environment was completely surrounded by the dextran molecular while that of groups 6.5 were encircled partially with a lower degree of glycation. Compared to β-conglycinin, groups 4.8 demonstrated a decreasing surface hydrophobicity and sulfhydryl group content while groups 6.5 increased. The secondary structure of β-conglycinin soluble at pH 4.8 after conjugating under macromolecular crowding environment tended to stretch out and the highly ordered structure turn to random structures. The differences between the extraction of pH 4.8 and pH 6.5 conjugated by dry-heating methods were not as remarkable as the difference between the extraction conjugated by macromolecular crowding environment.

Fabrication of Zein/Pectin Hybrid Particle-Stabilized Pickering High Internal Phase Emulsions with Robust and Ordered Interface Architecture

Diets containing partially hydrogenated oils (PHOs) expose the human body to trans fatty acids, thus endangering cardiovascular health. Pickering high internal phase emulsions (HIPEs) is a promising alternative of PHOs. This work attempted to construct stable Pickering HIPEs by engineering interface architecture through manipulating the interfacial, self-assembly, and packing behavior of zein particles using the interaction between protein and pectin. Partially wettable zein/pectin hybrid particles (ZPHPs) with three-phase contact angles ranging from 84° to 87° were developed successfully. ZPHPs were irreversibly anchored at the oil-water interface, resulting in robust and ordered interfacial structure, evidenced by the combination of LB-SEM and CLSM. This situation helped to hold a percolating 3D oil droplet network, which facilitated the formation of Pickering HIPEs with viscoelasticity, excellent thixotropy (>91.0%), and storage stability. Curcumin in HIPEs was well protected from UV-induced degradation and endowed HIPEs with ideal oxidant stability. Fabricated Pickering HIPEs possess a charming application prospect in foods and the pharmaceutical industry.

Development and Characterization of Multifunctional Gelatin-Lysozyme Films Via the Oligomeric Proanthocyanidins (OPCs) Crosslinking Approach

Herein, we report firstly the development of sustained antimicrobial and antioxidant gelatin-lysozyme films crosslinked by the oligomeric proanthocyanidins (OPCs), a duel-functional agent. Lysozyme release kinetic studies were performed at neutral and acidic pH, and they could be described as a biphasic process. OPCs crosslinking retarded lysozyme release at pH 7.0, in a dose dependent manner, and the inhibition zone tests confirmed that the sustained release of lysozyme was realized upon weak crosslinking with OPCs. OPCs crosslinking enhanced thermal stability of the gelatin films, and gave them the ability to barrier ultraviolet light. OPCs loadings endowed the films excellent antioxidant activities, the DPPH radical scavenging activity of the films increased linearly to 93.97% upon increasing OPCs loadings from 0 to 2.0%. Concomitantly, the reducing powder of the films increased linearly from 6.08 ± 0.09 to 45.53 ± 2.74 μmol Asc Acid/g film. Additionally, the antioxidant properties of gelatin films against lipid oxidation in edible oils were evaluated. Lipid hydroperoxides of algal oils in the gelatin bags were approximately a quarter of that in low-density polyethylene (LDPE)-based bags, and the malondialdehyde (MDA) values of algal oils were lower than that in LDPE-based bags by 1–2 orders of magnitude. Regrettably, the incorporation of OPCs did not enhance the antioxidant capability of gelatin films against lipid oxidation in wrapped edible oils, possibly due to the limited release toward algal oils in term of its oil-soluble attribute. This study opens a promising pathway for producing sustained antimicrobial and antioxidant gelatin films using a bi-functional agent.