Gelling and emulsifying properties of soy protein hydrolysates in the presence of a neutral polysaccharide

Kappa-carrageenan enhances the gelation and structural changes of egg yolk via electrostatic interactions with yolk protein

The effect of κ-carrageenan (κ-C) on yolk over heat-induced gelation at natural yolk pH (6.2) and natural whole egg pH (7.5) was studied. The results showed the zeta potential values changed from -2.3 to -31.3 mV, from -8.6 to -28.6 mV for native pH yolk and pH 7.5 yolk because of the κ-C addition, respectively. These results indicated electrostatic interactions formed between protein and κ-C. The average area of holes formed by yolk gelation increased by κ-C addition. The addition of 1.0% κ-C decreased the gelling points from 62.1 to 54.4 °C, from 64.5 to 61. 6 °C for native pH and pH 7.5 yolk, respectively. A schematic model was established to show that κ-C enhances the yolk properties via electrostatic interactions. And the Fourier transform infrared (FTIR) spectroscopy verified the formation of κ-C-protein interactions. This study provides a guidance for designing novel food systems containing yolk and κ-C.

Characterization of soy protein isolate/Flammulina velutipes polysaccharide hydrogel and its immunostimulatory effects on RAW264.7 cells

Soy protein isolate (SPI) is a nutritional commercial product, while the poor solubility and gelling restricts its applications for functional foods. To surmount the challenge presented by this poor solubility, the gelling polysaccharide shows potential in ameliorating SPI. In this study, SPI/Flammulina velutipes polysaccharide (FVP) hydrogels were prepared under four mixing ratios (32:1, 20:1,15:1 and 10:1, w/w) at both pH6.5 and pH3.5, respectively. The stability of hydrogels and its immunostimulatory impact on RAW264.7 cells were assessed. Initial results revealed that water holding capacity increased when increasing the mixing ratios, likely to be the results of enhanced electrostatic interaction between SPI and FVP. The addition of FVP contributed to the improved swelling ratio and lowered the degradation ratio. Such structure feature was shown to be favorable for hydrogels to culture cells. More importantly, SPI/FVP hydrogels demonstrated no cytotoxic effect on cell metabolic activity. The culture of SPI/FVP hydrogels enhanced the immunostimulatory capacity in RAW264.7 cells by increasing phagocytosis and inducing the production of pro-inflammatory cytokines. The performances of the hydrogels made at pH3.5 were superior to those prepared at pH6.5. Our results suggested SPI/FVP hydrogels may provide application potential for the development of functional foods.

Physicochemical and functional properties of goat milk whey protein and casein obtained during different lactation stages

During lactation, goat milk contains colostrum, transitional milk, mature milk, and end milk. The protein present in goat milk during different lactation periods has different characteristics. This study aimed to characterize the protein profile of goat milk samples obtained at different lactation stages and to identify changes in the physicochemical and functional properties of whey protein and casein from goat milk collected at 1, 3, 15, 100, and 200 d after calving. The results demonstrated that the lactation period had a great influence on the physicochemical and functional properties of goat milk whey protein and casein, especially the protein properties of colostrum on the first day after delivery. The denaturation temperature, hydrophobicity, and turbidity of whey protein were significantly higher on the first day postpartum than at other lactation periods. Correspondingly, the colostrum whey protein also had better functional properties, such as emulsification, oil holding capacity, and foaming properties on the first day postpartum than at other lactation periods. For casein, the turbidity, particle size, water holding capacity, and foaming properties on the first day after delivery were significantly higher than those at other lactation periods, whereas the denaturation temperature, oil holding capacity, and emulsification followed the opposite trend. For both whey protein and casein, the 2 indicators of emulsifying properties, namely, emulsifying activity index and the emulsion stability, also followed an opposite trend relative to lactation stage, whereas the changes in foaming capacity with the lactation period were completely consistent with the change of foaming stability. These findings could provide useful information for the use of goat milk whey protein and casein obtained during different lactation stages in the dairy industry.

Functional properties and antioxidant activity of gelatine and hydrolysate from deer antler base

Gelatine was extracted from deer antler base by the hot water method and hydrolyzed with trypsin. A comparison of the properties of gelatine before and after enzymatic hydrolysis showed a decline in the surface hydrophobicity, enhanced thermal stability, broadening of the particle size distribution, a zeta potential shift to a lower pH, reduced foaming and emulsifying properties, and enhanced antioxidant activity. Hydrolysis increased the gelatine antioxidant activity in DPPH and FRAP assays. These results indicate that the functional properties of deer antler base gelatine may be affected by trypsin modification.

Optimization of the Emulsifying Properties of Food Protein Hydrolysates for the Production of Fish Oil-in-Water Emulsions

The incorporation of lipid ingredients into food matrices presents a main drawback-their susceptibility to oxidation-which is associated with the loss of nutritional properties and the generation of undesirable flavors and odors. Oil-in-water emulsions are able to stabilize and protect lipid compounds from oxidation. Driven by consumers' demand, the search for natural emulsifiers, such as proteins, is gaining much interest in food industries. This paper evaluates the in vitro emulsifying properties of protein hydrolysates from animal (whey protein concentrate) and vegetal origin (a soy protein isolate). By means of statistical modelling and bi-objective optimization, the experimental variables, namely, the protein source, enzyme (i.e., subtilisin, trypsin), degree of hydrolysis (2-14%) and emulsion pH (2-8), were optimized to obtain their maximal in vitro emulsifying properties. This procedure concluded that the emulsion prepared from the soy protein hydrolysate (degree of hydrolysis (DH) 6.5%, trypsin) at pH 8 presented an optimal combination of emulsifying properties (i.e., the emulsifying activity index and emulsifying stability index). For validation purposes, a fish oil-in-water emulsion was prepared under optimal conditions, evaluating its physical and oxidative stability for ten days of storage. This study confirmed that the use of soy protein hydrolysate as an emulsifier stabilized the droplet size distribution and retarded lipid oxidation within the storage period, compared to the use of a non-hydrolyzed soy protein isolate.

Flocculation behavior and gel properties of egg yolk/κ-carrageenan composite aqueous and emulsion systems: Effect of NaCl

In this study, the influence of NaCl on the flocculation behavior and gel properties of egg yolk/κ-carrageenan mixed dispersions or emulsions were studied. As a result of NaCl incorporation, there was a decrease in the mean droplet size, zeta potential, degree of flocculation and viscosity of the mixed dispersions/emulsions, and the onset point of gelation was also brought forward. Increasing the concentration of NaCl led to a significant increase in gel strength and decrease in gel cohesiveness. Results from low field nuclear magnetic resonance (LF-NMR) confirmed that the addition of NaCl could significantly reduce the hydration ability of gel molecules and increase the content of immobilized water of hydrogels as the gel strength increased, while the water holding capacity of emulsion gels was depressed with the incorporation of oil. These findings suggested the flocculation state and gel properties of egg yolk/κ-carrageenan mixed dispersions/emulsions can be tailored by adjusting NaCl for food formulations.

Study on the Preparation and Conjugation Mechanism of the Phosvitin-Gallic Acid Complex with an Antioxidant and Emulsifying Capability

To develop a novel emulsifier with an antioxidant capacity, a phosvitin-gallic acid (Pv–GA) complex was prepared via a free-radical method. This emulsifier characterizes some key technologies. Changes in the molecular weight of the Pv–GA complex were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS–PAGE) and the matrix-assisted laser desorption/ionization time of light mass spectrometry (MALDI-TOF-MS). Fourier transform infrared spectroscopy (FTIR) indicated that C=O, C–N and N–H groups were also likely to be involved in the formation of the complex. A redshift was obtained in the fluorescence spectrogram, thereby proving that the covalent combination of Pv and GA was a free radical-forming complex. The results indicated that Pv and GA were successfully conjugated. Meanwhile, the secondary structure of Pv showed significant changes after conjugation with GA. The antioxidant activity and emulsifying properties of the Pv–GA complex were studied. The antioxidant activity of the Pv–GA complex proved to be much higher than that of the Pv, via assays of the scavenging activities of 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals and because of their ability to reduce power. The emulsification activity of the Pv–GA complex was also slightly higher than that of Pv. To function with the most demanding antioxidant and emulsification activities, the optimum conjugation condition was Pv (5 mg/mL) conjugated 1.5 mg/mL GA. Furthermore, the mechanism of Pv–GA conjugation was studied. This study indicated that GA could quench the inner fluorescence of Pv, and this quenching was static. There was a strong interaction between GA and Pv, which was not obviously affected by the temperature. Furthermore, several binding sites were close to 1, indicating that there was an independent class of binding sites on Pv for GA at different temperatures. The conjugation reaction was a spontaneous reaction, and the interaction forces of GA and Pv were hydrogen bonds and van der Waals force.

Microparticles, Microspheres, and Microcapsules for Advanced Drug Delivery

Microparticles, microspheres, and microcapsules are widely used constituents of multiparticulate drug delivery systems, offering both therapeutic and technological advantages. Microparticles are generally in the 1–1000 µm size range, serve as multiunit drug delivery systems with well-defined physiological and pharmacokinetic benefits in order to improve the effectiveness, tolerability, and patient compliance. This paper reviews their evolution, significance, and formulation factors (excipients and procedures), as well as their most important practical applications (inhaled insulin, liposomal preparations). The article presents the most important structures of microparticles (microspheres, microcapsules, coated pellets, etc.), interpreted with microscopic images too. The most significant production processes (spray drying, extrusion, coacervation, freeze-drying, microfluidics), the drug release mechanisms, and the commonly used excipients, the characterization, and the novel drug delivery systems (microbubbles, microsponges), as well as the preparations used in therapy are discussed in detail.