Mechanism of galacturonic acid-rich Schisandra Chinensis polysaccharide in improving emulsifying properties of soy protein hydrolysate: Insights from interfacial behavior and molecular interactions.

Limited hydrolysates ranging from 6.82 to 16.74 % degree of hydrolysis (DH) were produced from palm kernel expeller protein (PKP) using Alcalase. The nutritional value, physicochemical and functional properties of PKP and the hydrolysates, especially effects of DH, pH, ionic strength and temperature on these properties were studied. Results showed that all the hydrolysates showed higher nutritive value, better thermal stability and solubility (70.68–99.13 g/100 g) than PKP. The surface hydrophobicity, emulsifying properties and foaming activity were improved by limited enzymatic hydrolysis (DH: 6.82 to 11.72 %), whereas the foam stability, viscosity, water and oil holding capacity were negatively correlated with DH. Increase in ionic strength (from 0 to 0.4 mol/L) or temperature (from 30 to 50 °C) enhanced the solubility, emulsifying properties and foaming activity. But high temperature remarkably weakened the foaming properties and viscosity. Solubility, surface hydrophobicity and molecular weight influenced the emulsifying and foaming properties. PKP and the hydrolysates were good protein source.

Azo dyes are made in significant amounts annually and released into the environment after being employed in the industry. There are some reports about the toxic effects of these dyes on several organisms. Thus, the textile dye Reactive Black 5 (RB5) has been examined for its cytotoxic effects on the human serum albumin (HSA) structure. Molecular interaction between RB5 and HSA indicated the combination of docking methods, molecular dynamic simulation, and multi-spectroscopic approaches. HSA's intrinsic fluorescence was well quenched with enhancing RB5 level, confirming complex formation. Molecular dynamics (MD) simulation was done to study the cytotoxic effects of RB5 and HSA conformation. Molecular modeling revealed that the RB5-HSA complex was stabilized by hydrogen bonds and van der Waals interactions. The results of molecular docking revealed that the binding energy of RB5 to HSA was - 27.94kJ/mol. The change in secondary structure causes the annihilation of hydrogen bonding networks and the reduction of biological activity. This research can indicate a suitable molecular modeling interaction of RB5 and HAS and broaden our knowledge for azo dye toxicity under natural conditions.

Protein properties can be modified by selective enzymatic hydrolysis. In this study, the alkaline metalloendopeptidase AprX (Serralysin; EC 3.4.24.40) from Pseudomonas paralactis was used for the tailored hydrolysis of different food proteins resulting in the production of protein hydrolysates with improved emulsifying properties. Sodium caseinate, wheat gluten and buffalo worm protein were used for AprX hydrolysis at 40 °C and pH 8 to cover a spectrum of different protein sources. A maximum degree of hydrolysis (DH) of 13.1 ± 0.2%, 14.2 ± 0.1% and 20.7 ± 0.1% was reached for sodium caseinate, wheat gluten and the worm protein, respectively. The corresponding hydrolysate properties were analyzed regarding their particle size, peptide composition, solubility, viscosity, surface hydrophobicity and interfacial tension. The emulsifying properties were investigated by the oil-droplet size, ζ-potential and stability of emulsions prepared from the hydrolysates. Using partially hydrolyzed sodium caseinate (DH = 10.6%) as an emulsifier lead to an eightfold increase of the emulsion stability (t1/2 = 180 ± 0 min) compared to unhydrolyzed sodium caseinate. The emulsion stability using wheat gluten hydrolysates (DH = 11.9%) was increased 30-fold (t1/2 = 45 ± 5 min). Simultaneously, the solubility of gluten was increased by 60%. Buffalo worm hydrolysates (DH = 14.6%) had a twofold (t1/2 = 85 ± 5 min) increased emulsion stability. In conclusion, AprX can be used to improve the solubility and emulsifying properties of food proteins at a relatively high DH.

<p indent="0mm">Self-assembly of nanoparticles using suspended droplets as carriers is an important means to prepare high-quality nanostructures. To study the dynamic behavior of self-assembly of nanoparticles in suspended droplets, CuO nanoparticles were considered as an example. The molecular dynamics simulation method was used to study the dynamic processes of particle agglomeration, spontaneous migration of particles to the surface of the suspended droplets, and self-assembly of particles on the surface of the droplets. The effects of van der Waals interaction strength between particles, particle concentration, and particle wettability on the agglomeration, migration and self-assembly behavior of particles were analyzed. The mechanism of agglomeration and self-assembly of nanoparticles in suspension droplets was revealed. Results show that nanoparticles in the suspended droplets agglomerate under the action of van der Waals force, electrostatic force, and thermal motion of water molecules. The stronger the hydrophobicity of the nanoparticles, the easier the particles migrate spontaneously to the gas-liquid interface. At particle concentrations of 7%–19%, the migration rate of hydrophobic particles <italic>θ</italic>&gt;90° is more than 90%, while strongly hydrophilic particles (<italic>θ</italic>&lt;30°) almost do not migrate. When the particles migrate to the gas-liquid interface and the interaction between the particles is weak, the following phenomenon is observed: as the enrichment of the particles at the interface increases, the self-assembled structure of the particles changes from gas-like distribution to liquid-like distribution and a single-layer smectic nanofilm and a curved nanostructure form locally. As the van der Waals interaction between the particles increases, the area of the self-assembled film increases first and then decreases. When the strength of van der Waals interaction between particles (<italic>ε</italic>_{<italic>n</italic>}_-_{<italic>n</italic>}) is 0.25 kcal/mol, the film area is the largest. The higher concentration of hydrophobic nanoparticles effectively guarantees that more particles migrate to the gas-liquid interface, and the moderate van der Waals interaction strength between particles makes it easier for nanoparticles on the surface of suspended droplets to self-assemble to form ordered and large-area high-quality nanostructures.

Interfacial behavior of cyclodextrins at the oil-water interface of Pickering emulsion

Plant cell adhesion to polymer surfaces as predicted by a thermodynamic model and modified by electrostatic interaction

Plant cell adhesion to polymer surfaces as predicted by a thermodynamic model and modified by electrostatic interaction

Impact of molecular composition and sequential aqueous-phase exchange on polyglycerol polyricinoleate interfacial behavior.

The effect of enzymatic treatment of a sunflower protein isolate on the rate of adsorption at the air–water interface

Due to the favorable properties and versatility, the applications of ionic liquids (ILs) have been introduced in petroleum industry for different purposes including Enhanced Oil Recovery (EOR) processes. The ability of ILs to alter surface behavior of surfactant molecules by producing specific interactions with surfactant has motivated further investigation on its application to the important chemical EOR mechanisms, such as surface and interfacial tension lowering under reservoir conditions. The mixtures of in-house surfactant and different types of ILs (imidazolium- and eutectic-based ILs) as additives were formulated using different concentration ratio and prepared in fixed brine salinity. The surface tension (ST) and interfacial tension (IFT) behavior of the formulated mixtures were investigated by performing pendant and spinning drop tests at ambient and high temperature. In general, the extent of ST and IFT reduction was dependent on the type and concentration of ILs. The presence of ILs was able to lower both ST and IFT of surfactant solution and its effect as a function of ILs concentration was found to be more pronounced at high temperature. Of all ILs, eutectic-based IL showed the highest ability to decrease ST at any concentration used. Similarly, the eutectic-based IL was also regarded as the best ILs in lowering the surfactant solution/oil IFT even in the use of low concentration. From this study, it can be concluded that ILs can be proposed as new additives to alter the surface and interfacial behavior which are taking place through some surfactant-IL interactions and eventually improve surfactant performance in reducing ST and IFT. Surfactant solution with a lower ST due to the addition of ILs is expected to provide promising performance for surfactant-based EOR process involving gas mobility control application leading to enhancement of sweep efficiency, while a lower IFT value can provide favorable conditions for better oil displacement efficiency.

The interaction of Naphthol Yellow S (NYS) with pepsin: Insights from spectroscopic to molecular dynamics studies

In this contribution, we have determined the effect of limited enzymatic hydrolysis on the interfacial (dynamics of adsorption and surface dilatational properties) and foaming (foam formation and stabilization) characteristics of a soy globulin (beta-conglycinin, fraction 7S). The degree of hydrolysis (DH = 0, 2, and 5%), the pH of the aqueous solution (pH = 5 and 7), and the protein concentration in solution (at 0.1, 0.5, and 1 wt %) were the variables studied. The temperature and the ionic strength were maintained constant at 20 degrees C and 0.05 M, respectively. The rate of adsorption and surface dilatational properties (surface dilatational modulus, E, and loss angle) of beta-conglycinin at the air-water interface depend on the pH and DH. The adsorption decreased drastically at pH 5.0, close to the isoelectric point of beta-conglycinin, because of the existence of a lag period and a low rate of diffusion. The interfacial characteristics of beta-conglycinin are much improved by enzymatic treatment, especially in the case of acidic aqueous solutions. Hydrolysates with a low DH have improved functional properties (mainly foaming capacity and foam stability), especially at pH values close to the isoelectric point (pI), because the protein is more difficult to convert into a film at fluid interfaces at pH approximately equal to pI.

Keywords: Emulsion, flocculation, bridging, saliva, salivary protein, salivary peptides, lysozyme, -lactoglobulin, complex formation, LC-MS, SELDI-TOF-MS, proteomics. Upon consumption food emulsions undergo various structural and compositional changes in the mouth. One of these changes is that mixing of an emulsion with saliva induces droplet flocculation In the study described in this thesis we investigated the influence of saliva on emulsions properties, the mechanism of flocculation and the role in sensory perception. Firstly, we started with evaluating the effect of parameters related to emulsions on flocculation (i.e. differently charged surfactants and proteins such as -lactoglobulin and lysozyme used as emulsifiers and oil-volume fraction). Among the obtained results, we observed that the sign and the density of the charge on the surface of the droplets determine the (ir-)reversibility of flocculation upon dilution with water and shearing. Secondly, the effect of saliva-related parameters was analyzed. Among other aspects, it appeared that an increase in salivary protein concentration increased emulsion flocculation, and that extensive flocculation is typically found for unstimulated saliva. This approach shows that both emulsion and saliva properties affect the flocculation behavior of emulsions/saliva mixtures. To investigate the nature of the flocculation, we characterized the salivary protein composition in both the continuous phase of the emulsion/saliva mixture and on the emulsion droplets. Different physical-chemical and biochemical techniques were used. For this approach, we focused on -lactoglobulin and lysozyme stabilized emulsions, which flocculated reversibly and irreversibly, respectively, upon mixing with saliva. A large number of salivary proteins and peptides in the molecular mass (Mr) range between 0.8 kDa and 100 kDa and the salivary mucins MUC5B and MUC7 (Mr > 200 kDa) associated with emulsion droplets of the emulsions. The results also indicate that the emulsifying protein at the oil-water interface determines which salivary components associate with the droplets in the flocs. A hypothesis is formulated that emulsion flocculation is mainly driven by a complex formation involving specific interactions and electrostatic attraction between salivary peptides/proteins and the emulsifying proteins at the droplets surface. The importance of the saliva-induced droplet flocculation was demonstrated with a sensory paneling study. Emulsions stabilized by whey protein isolate, (predominantly composed of -lactoglobulin) showed reversible flocculation and were perceived as creamy. In contrast, emulsions stabilised by lysozyme showed irreversible flocculation and were perceived as dry, rough and astringent. To conclude, this thesis shows that saliva-induced emulsion flocculation is driven mainly by association of salivary peptides and proteins to the droplets surface. Because of this, flocculation is determined by the composition of the droplet interface as well as the composition of the saliva, and can be controlled by variation of emulsion parameters (charge, pH, ionic strength). This interaction between emulsions and saliva may help to improve our understanding an control the sensory perception of emulsions.

Dual-responsive emulsion system: Unraveling pH and host-guest interactions for emulsion stability and enhanced oil recovery

Interfacial and emulsifying behaviour of crayfish protein isolate