Salt and pH-Induced Attractive Interactions on the Rheology of Food Protein-Stabilized Nanoemulsions

Abstract

This research aimed to investigate the possibility of forming gelled nanoemulsions (NEs) by inducing attractive interactions among the nanodroplets. The effect of salt concentration and changes in pH on the stability and gelation behavior of 2, 4, and 5% sodium caseinate (SC) and whey protein isolate (WPI)-stabilized 40% canola oil-in-water NEs were investigated. For the effect of salt, sodium chloride was added in a concentration of 0.1, 0.5, and 1 M in the continuous phase of the NEs at neutral pH, whereas to study the effect of acidification, the pH of the NEs was adjusted to the isoelectric point (pI) of the proteins. The addition of salt led to attractive gelation in WPI NEs because of a screening of charge. In contrast, the gel strength of SC-stabilized NEs was reduced with salt, which was attributed to the loss of close packing of droplets and their surrounding repulsive barriers because of charge screening and to the steric barrier of interfacial SC preventing droplet aggregation. All the NEs with pH at the pI of proteins transformed into strong attractive gels made of droplet aggregates irrespective of the type or concentration of protein because of the complete charge neutralization. The strength of the acidified NE gels increased with a decrease in droplet size and the type of protein used. Overall, research on the effect of different environmental factors on the stability and gelation behavior of protein-stabilized NEs could be useful for possible applications of these nanoscale materials in various food systems.

Essentials in saline pharmacology for nasal or respiratory hygiene in times of COVID-19

“…Charge shielding of mucin or mucin-like macromolecules that consequently undergo gelation, stabilizing ALF/air interface and reducing its breakup, resulting in a reduced tendency of the ALF to disintegrate into very small droplets Saline droplets (emulsion) [31] Mechanistic study of NaCl droplets ± surfactant Added to nanoemulsions, NaCl makes finer micellar droplets "aggregate", making the droplet size distribution to move to a bigger size range (so will lead to faster deposition), while surfactant in contrast breaks up the droplets to smaller sizes Saline phospholipid droplets [32] Mechanistic study of effect of NaCl on phospholipid vesicles and bilayers -Na + and Cl − binds with the lipid head and induces strong hydrophobic repulsion on the lipid tail -This leads to enhanced hydrophobic repulsion on lipids and so forces lipids to attach firmly on the surface substrate Much larger external energy is needed for vesicle formation in salt solutions than in pure water Sodium chloride aerosol [35] Mechanistic study of NaCl and corn oil (bio)aerosol on filtration by face mask materials (FFP1, N95, P100, and elastomeric half-mask respirators)…”

Essentials in saline pharmacology for nasal or respiratory hygiene in times of COVID-19

“…Table 3 summarizes a number of recommendations, based on the results from this analysis, for use of saline for nasal and/or respiratory hygiene at initial onset of common cold symptoms, which clinically overlap with COVID-19 upper respiratory symptoms. While isotonic seawater has a rinsing effect improving the MCC [[134]], the use of pure isotonic saline is rather proposed, because nasal spray compositions with more (buffering) ions such as seawater, or with surfactants, emulsi ers, and/or active substances may not necessarily lead to the desired effects, such as observed with pure saline on SARS-CoV-2 replication in vitro [33,93]; moreover, the addition of surfactants/emulsi ers may enhance bio-aerosol formation [31,39], while these products or active substances may inhibit the ciliary beating [85] or be ciliotoxic (e.g. polyvidone-iodine [134,[135]]).…”

“…From a mechanistic focus, it is proposed that isotonic saline inhalation changes surface tension of the liquid lm on the airway epithelium, leading to less droplet formation and, as such, to less release of exhaled bio-aerosols [13]. In vitro, saline induces droplet aggregation and stronger gel formation leading to faster deposition, while surfactant in contrast breaks up the droplets to smaller sizes [ [38], [39]]. Salinity in evaporated respiratory droplets also affects the structure of virus particles and viral decay, whereas processes at the air-liquid interface drive the inactivation of viruses in droplets [ [40], [41]].…”

How an organogelator can gelate water: gelation transfer from oil to water induced by a nanoemulsion

“…This could indicate that there is some cohesive part in the nanoemulsion that we can assume to be a strong interaction between the droplets. [31][32][33] Further characterization of the nanoemulsion was then achieved by dynamic and static light scattering (DLS, SLS), small angle X-ray scattering (SAXS), cryo-scanning electron microscopy (Cryo-SEM), and transmission electron microscopy (TEM).…”

“…PIT emulsification is based on the changes in the solubility (curvature) of surfactants depending on the temperature. [33][34][35][36][37] For example, nonionic surfactants of the polyoxyethylene kinds are hydrophilic and soluble in water at low temperatures. 30 When the temperature is raised, they turn lipophilic and become more soluble in the oil phase.…”