Cuihua Chang

Protection of β-carotene from chemical degradation in emulsion-based delivery systems using antioxidant interfacial complexes: Catechin-egg white protein conjugates

The aim of the present study was to fabricate catechin-egg white protein (CT-EWP) conjugates as novel food-grade antioxidant emulsifiers designed to improve the physicochemical stability of β-carotene (BC) emulsions. CT-EWP conjugates were synthesized using free radical grafting, and the formation of conjugates was confirmed by electrophoresis and liquid chromatography-mass spectrometry. The physicochemical stability of BC emulsions was characterized by measuring alterations in particle size, ζ-potential and BC retention. The particle size and ζ-potential changed more rapidly at 37°C than at 4 or 25°C, however no creaming or oiling-off were observed at any of the storage temperatures, suggesting all emulsions were physically stable throughout the 30-day storage period. Compared to emulsions stabilized by EWP or CT+EWP physical mixtures (no conjugation), CT-EWP conjugate-stabilized emulsions had better resistance to environmental stresses, such as thermal processing and high ionic strengths, which was attributed to a stronger steric repulsion between the oil droplets. CT-EWP conjugates also significantly reduced the degradation rate of BC in emulsions during storage (p<0.05), which was attributed to their strong antioxidant and interfacial activities. These results indicate that CT-EWP conjugates can be utilized to develop food-grade delivery systems to protect chemically labile lipophilic bioactive compounds.

Separation of bovine hemoglobin using novel magnetic molecular imprinted nanoparticles

Magnetic molecular imprinted nanoparticles (MMIPs), combining the progressiveness of magnetic nanoparticles and surface molecular imprinting technology, have attracted increasing attention because of the high efficiency and specificity in isolation and enrichment of the target protein. This study focused on the preparation of bovine hemoglobin MMIPs with bovine hemoglobin (BHb) as the template protein and the molecular imprinted polymer covering the functional magnetic nanoparticles modified with silane and acrylic groups. The physicochemical characteristics as well as the dynamics and isothermal adsorption properties of the generated nanoparticles were investigated to determine their efficiency and specificity in the adsorption of target protein. The maximum adsorption of the target protein was 169.29 mg g−1 at a specific pH, which was much larger than those obtained in some other research reports. MMIPs showed favorable selectivity towards BHb in a mixture of three different proteins. The results indicated the significant effects and broad prospects of MMIPs in the isolation and enrichment of specific proteins in the field of food, medicine and biological research.

Molecular forces and gelling properties of heat-set whole chicken egg protein gel as affected by NaCl or pH

Effects of NaCl concentrations and pH on the intermolecular forces and gel properties of whole chicken egg protein dispersions were studied via solubility, surface hydrophobicity, intermolecular forces, texture analysis, low-field nuclear magnetic resonance (LF-NMR) and colour analysis. Results showed that the intermolecular forces involved in the formation of egg gel were regulated by NaCl/pH. The results of gel fracture analysis suggested that the changes of fracture strength and strain were closely related with the internal balance of gel molecular forces. Moreover, a negative/positive correlation existed in the free water/bound water relaxation proportion and fracture strength. These findings provide an important theoretical basis for the innovation of heat-induced egg gel products.

Films Based on Egg White Protein and Succinylated Casein Cross-Linked with Transglutaminase

Transglutaminase (TGase) and succinylation could modify the physicochemical characteristics and the functional properties of proteins. The aim of this work was to cross-link egg white protein (EWP) and succinylated casein with TGase and to assess the feasibility of making a novel composite protein film. The effects of succinylated casein content, reaction time, and TGase concentration on the mechanical properties, physical characteristics (thermal property and degree of crystallinity), and structure properties (secondary structure and surface micrograph structure) of the film were investigated in this study. The results revealed that the susceptibility of EWP to TGase-mediated cross-linking modification was enhanced by succinylated casein. Meanwhile, the films with TGase were more homogeneous and smoother and possessed better water resistance and thermal stability. The content of α-helix, β-turn structures were increased whereas β-sheet structure was decreased. The spatial conformation and degree of crystallinity of composite protein film were also affected by TGase. The increase of the degree of crystallinity of the composite film further proved the improvement of film mechanical properties induced by TGase and succinylated casein. Based on the above results, this study provides relevant data and insights for the TGase/chemical modification of protein-based edible films.