Food Hydrocolloids最新文献

Mungbean and lentil proteins are gaining attention for the production of high moisture extrusion (HME)-based meat- and dairy-analogues. However, understanding the mechanism of fibrous structure formation and molecular and higher-order changes in HME remains limited. Globulin protein isolates from mungbean (MBPI), green lentil (GLPI) and yellow pea (YPPI) along with commercial soy (CSPI) and yellow pea (CPPI) protein were investigated for their pasting properties using high-pressure rapid visco analyser (RVA), and the formation of anisotropic structures and molecular changes at constant HME conditions. Vicilin-rich MBPI showed higher viscosity on RVA, consumed higher specific mechanical energy (SME) during extrusion, and developed extrudates with higher textural strength and cutting force than proteins with both legumin and vicilin-like globulins, i.e. GLPI and YPPI. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and size-exclusion chromatography (SEC) of extrudates' soluble proteins showed dissociation of vicilin-like globulins into their smaller subunits. In contrast, legumin-like globulins were reaggregated into higher molecular weight soluble macromolecules. Further, SDS-PAGE of extrudates’ total protein revealed the involvement of legumin-like globulin in the macrostructure network of the extrudates. During HME, native unfolded structures were destroyed with conversion, predominately driving changes in the tertiary structure (thermal denaturation) and secondary structure with loss of helical structure to formation of random coil and beta-sheet structures. Protein extractability in different solvents was greatly reduced, with covalent and non-covalent interactions being majorly involved in the stabilisation of extrudates structure. Protein composition, and in particular vicilin-legumin ratio and protein conformation, determined the structural development and molecular changes in HME.

Resveratrol (RES) has attracted much attention because of its many potential health benefits. However, its poor aqueous solubility and chemical instability hinder its application. In this study, ovalbumin (OVA) fibrils (OVAF) were used as nanocarriers to improve the aqueous solubility, thermal stability and antioxidant activity of hydrophobic RES, and the effects of pH were also investigated. The results showed that after complexation with OVAF at pH 2.0, the aqueous solubility of RES was 12.3 times higher than that of free RES. Transmission electron microscope images revealed that after incorporating with RES, the OVAF assembled into entangled aggregates due to the interaction. Intrinsic fluorescence spectra, Fourier transform infrared spectra and zeta potential measurements showed that the hydrophobic interactions, hydrogen bonds and electrostatic interactions were mainly contributed to the formation of OVAF/RES complex. Moreover, X-ray diffraction results proved that RES was encapsulated in fibrils with an amorphous form. It was noteworthy that OVAF at pH 2.0 had the highest binding constant with RES, and thus it exhibited the best protective effect on thermal degradation of RES. In addition, the antioxidant capacity of RES was drastically improved through the complexation with OVAF. Hence, these results suggested that OVA amyloid-like fibrils may be a suitable nanocarriers for hydrophobic nutrients.

The effect of enzymatic dephosphorylation, using intestinal alkaline phosphatase, on the structure of casein micelles in caprine micellar casein concentrate (MCC) was studied. An optimal condition, involving preheating the MCC dispersion, pH 6.4, 2.5 mg casein/mL and 0.4 U phosphatase/mL, was established and used to prepare MCC with 0–49% dephosphorylation by incubation at 37 °C for 0–180 min. β-Casein showed marked dephosphorylation and formed multi-phosphorylated isoforms depending on dephosphorylation degree, whereas α_s- and κ-caseins showed limited and fast dephosphorylation, respectively. With increasing dephosphorylation, both the colloidal calcium and the calcium sensitive micellar caseins, especially β-casein, were gradually dissociated, and the calcium insensitive serum κ-casein was gradually associated with the micelles. The dissociated β-casein fraction was predominated by isoforms with lower number of phosphate groups. For micelles with increasing dephosphorylation, the molar mass decreased, the gyration and hydrodynamic radii decreased, the ratio of gyration to hydrodynamic radii and micellar hydration increased, the spherical morphology was generally retained, and the internal protein inhomogeneity disappeared progressively. These results suggest that after dephosphorylation, the caprine micelle framework underwent an intra-micellar mass redistribution, and become more loose and homogeneous.

The interfacial adsorption properties of colloidal particles were critical to the formation and stability of Pickering emulsions. This study aimed to improve the surface hydrophobicity, adsorption properties of Zein nanoparticles (ZN) by using the hydrophobic substance Medium-chain triglyceride (MCT) to form hybrid nanoparticles (ZMN). We investigated the impact of varying Zein/MCT ratios on the interfacial stabilization mechanism of Pickering emulsions and deciphered the relationship between adsorption properties, the rheological behavior of interfacial layer, and emulsion stability. Results revealed that the surface hydrophobicity of nanoparticles affected their adsorption properties as well as the rheological behavior of the composite interface. Specifically, an increase in the Zein/MCT ratio promoted the exposure of hydrophobic groups, increased the surface hydrophobicity of ZMN. This further led to an enhanced diffusion ZMN from the aqueous phase to the interface (K_diff increased from 0.033 mNm⁻¹s^−0.5 to 0.095 mNm⁻¹s^−0.5) and the rate of rearrangement at the interface (K_R increased from −0.016 mNm⁻¹s^−0.5 to −0.009 mNm⁻¹s^−0.5) which resulted in rapid adsorption and densely accumulation of ZMN at the interface. Furthermore, the adsorption properties of the nanoparticles directly influenced the viscoelastic and strain properties of the interfacial layer. The interfacial layer composed of ZMN exhibited enhanced viscoelasticity, increasing from 4 mN/m to 7 mN/m at low frequencies and from 6.8 mN/m to 12.5 mN/m at high frequencies. It also exhibited lower viscous dissipation and a stronger deformation response under varying external pressures. As a consequence, the rate and extent of droplet aggregation in ZMN stabilized emulsions (ZMNPEs) were reduced, attributing to the high viscoelasticity as well as the strong strain response of the interfacial layer. This research not only introduces a novel strategy to enhance the stability of Pickering emulsions using Zein-MCT composite nanoparticles, but also deepens our understanding of the interplay between particle adsorption properties, interfacial rheology, and emulsion stability.

Oat protein isolate (OPI) has high nutritional value but poor emulsifying properties. The purpose of modifying the OPI with high methoxyl pectin (HMP) was to improve emulsification. In this work, an oat protein isolate (OPI)–high methoxyl pectin (HMP) complex was constructed by changing the pH, and the interactions, formation mechanism and potential use of the OPI–HMP complex as a food emulsifier were explored. The presence of HMP caused structural changes in the OPI, and the changes were pH dependent. When the OPI to HMP mass ratio was 3:1, the critical pH for the phase behavior of OPI–HMP was 5.0. When the pH was greater than 5.0, the OPI and HMP were codissolved in the composite system mainly through electrostatic repulsion. When the pH was 5.0, a soluble OPI–HMP complex was formed by a combination of electrostatic attractions, hydrophobic interactions and hydrogen bonding. At pH values below 5.0, other aggregates of HMP and OPI were generated through electrostatic attraction and hydrogen bonding and formed insoluble aggregates. When the OPI to HMP mass ratio was 3:1 and the pH was 5.0, the particle sizes of the emulsion were the smallest at 8.75 μm due to the strong electrostatic interactions. The emulsification activity and stability were much higher than those of the OPI, and they formed dense osmotic networks, which protected the curcumin. The rates for curcumin encapsulation and retention reached 83.87 ± 1.50% and 88.70 ± 2.50%, respectively, and the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging rate was maintained at a high level (approximately 72%). These results confirmed the possibility of using the OPI-HMP complex emulsions as excellent and stable nutraceutical delivery systems for lipid soluble bioactive compounds in food and biomedical applications.

Fabrication of electrospun nanofibers by blending casein with electrospinnable polymers and/or additives is well reported. However, the electrospinnablility of pure casein has not been described due to the tendency of casein proteins to self-aggregate and form large colloidal structures. Here we analyze the influence of pH, ethanol content, ionic environment, and casein concentration on the solubility, solution viscosity, surface tension, and conductivity of casein-based spinning dopes. Further, the influence of casein dope characteristics on our ability to electrospin bead-free nanofibers was evaluated. A homogenous dispersion of casein was observed for mixtures with 20 wt % casein prepared using 60 % ethanol/water mixture at pH_eth 10. A minimum number of bead defects (BN, 6 × 10⁻³/μm²) and bead area (BA, 8.7 × 10⁻²) with minimum average fiber diameter (FD, 424 nm) and porosity (52 %) were observed for casein fibers fabricated using dopes containing 2 wt % of tetrasodium pyrophosphate (TSPP) on a casein basis. Further, the viscosity dependence on casein concentration at constant relative TSPP content was like that expected for a polyelectrolyte, and bead-free nanofibers were obtained at a concentration ∼2.5 times the entanglement concentration (C_e). Our results indicate that micellar dissociation is a necessary condition for the electrospinning of casein-only fibers free of beads and other polymers to fabricate novel biodegradable, and biocompatible, casein-based nanostructured mats, with the potential for food, cosmetic, packaging, and biomedical applications.

Liquid Egg yolk (LEY) tend to aggregate during pasteurization and lead to pipe blockage, which has become a thorny problem in food industry. In this paper, the mechanism of two common amino acid osmolytes (betaine and proline) delaying thermal aggregation of LEY was investigated. The result showed that addition of 3% betaine or proline improved thermal denaturation temperature of LEY in rheology and also reduced its viscoelasticity. The addition of amino acid shrinked particle size distribution of LEY. Betaine LEY (BLEY) had strong surface hydrophobicity while proline LEY (PLEY) had excellent solubility, both of which maintained its emulsifying property. Scanning electron microscopy (SEM) revealed that BLEY and PLEY had more porous surfaces, and the structure was more loose compared with LEY at the same temperature. The relaxation time T₂ indicated that betaine and proline can alleviate conversion of free water to immobilized and bound water during heat treatment process, thereby reducing the degree of thermal aggregation and viscosity. Fourier transform infrared spectroscopy (FT-IR) demonstrated the tendency of α-helix transformed to β-sheet as heating progress. Compared with LEY, the structure of BLEY and PLEY was more ordered, suggesting that orderliness of structure was the foundation for delaying thermal aggregation. In conclusion, this study provided a new idea and theoretical basis for production of heat-resistant LEY.

One of the possible advantages of protein fibers in composites is that they can interact with the continuous gel matrix as active fillers at neutral pH. This study aimed to investigate the impacts of short (SAF) and long amyloid fibrils (LAF) and ionic strength (0–150 mM NaCl) on the whey protein isolate (WPI)-based fiber-hydrogel composites. The water holding capacity of the composite gels more depended on the gel coarseness rather than their elasticity. Significant differences were observed between the rheological data of the SAF-WPI and LAF-WPI composites, and the maximum elastic modulus (G′) was achieved at 100 mM NaCl where the LAF-WPI composites outperformed the SAF-WPI ones in enhancing G′ and hardness. Nevertheless, the elasticity and hardness of the composites dramatically dropped at 150 mM NaCl due to the change in the gel microstructure from fine strand to particulate, according to CLSM and SEM images. Interestingly, the trend in average particle size changed at 150 mM NaCl for the SAF- and LAF-WPI soluble aggregates compared to the WPI soluble aggregates. The effects of amyloid fibril and NaCl concentration on the protein aggregates as the initial building blocks of the gel were confirmed by size exclusion chromatography. These results indicated that the properties of composite gel were related to the balance between aggregate creation and the development of cross-links between them during gelation. The findings of the current study could be exploited to predict the functional behavior of globular protein gels containing amyloid fibrils with different lengths at various NaCl concentrations.

Meat is prone to microbial contamination during storage, resulting in a shortened shelf life. To address this issue, absorbent preservation mats have been suggested and proven effective in slowing down the spoilage of meat. To this end, this study developed a novel bioactive sponge mat composed of oxidized bacterial cellulose (OBC) and microcapsules loaded with cinnamon essential oil (CGCM) obtained by complex coacervation of chitosan and gum Arabic. The surface charge of such microcapsules was regulated through the use of chitosan obtained from different deacetylation degrees. The physicochemical properties, antioxidant properties, and antibacterial properties of the OBC-CGCM sponge mats were investigated and their effect on meat preservation was assessed. The results concurred that the electrostatic interaction and hydrogen bonding between the CGCM and OBC sponge mat matrix led to improved thermal stability, water absorption, and tensile strength of the sponge mat. Furthermore, it demonstrated high antioxidant (reaching up to 90%) and antibacterial properties, particularly in the gas phase (up to 65%). The application of the prepared sponge mat to the preservation of meat was able to maintain the freshness and extend the shelf life of meat from 4 days to around 10 days under 4 °C, which is significantly better than that shown by commercially available preservation mats. In conclusion, the OBC-CGCM sponge mats are highly promising for meat preservation, thereby offering an attractive universal approach to constructing active biomass packaging materials.

The current study aimed to prepare the complexes between debranched-waxy corn starch and chitosan polymers (DBS-CS), and then investigated their corresponding structural characteristics, rheological property and potent application in Pickering emulsion. The results indicated that the existence of chitosan significantly inhibited starch short-range molecular rearrangement for all DBS-CS samples, which was manipulated by both debranching treatment and chitosan content. Interestingly, this is the first study to reveal that the outstanding peak at 1.8 ppm in ¹H NMR spectrum for sample DBS-CS was gradually shifted towards a lower-field region following an increased chitosan content. Moreover, the debranching treatment shifted the crystallinity pattern from A-type to B-type and the relative crystallinity of DBS-CS decreased gradually with the increased content of CS. All samples had a pseudoplastic fluid and shear-thinning behavior with an enhanced shear resistance following the complexation. The DBS-CS was applied in a Pickering emulsion for showing a greater emulsifying stability and a lower gel strength than native NS-CS prepared emulsion. Importantly, the encapsulation ability of curcumin in the DBS-CS emulsion was significantly improved, followed by an increase of 15.45% for its corresponding bioavailability compared to the control. Therefore, this study might highlight a potential carrier for delivering the bioactive substances in a green pattern.