Exploiting Salt Induced Microphase Separation To Form Soy Protein Microcapsules or Microgels in Aqueous Solution

Abstract

Self-assembly of native glycinin at room temperature was investigated as a function of the pH and the NaCl concentration. Microphase separation leading to the formation of dense protein microdomains was observed by confocal laser scanning microscopy. Depending on the conditions, the microdomains coalesced into a continuous protein rich phase or associated into large clusters. Addition of β-conglycinin inhibited phase separation and reduced the pH range in which it occurred. Microdomains of glycinin that were formed in the presence of 0.1 M NaCl transformed into hollow stable cross-linked microcapsules when heated above 60 °C with diameters between 3 and 30 μm depending on the protein concentration and a shell thickness between 1.0 and 1.4 μm. The microcapsules were stable to dilution in salt free water, whereas microdomains formed at room temperature redispersed. Microdomains formed in mixtures with β-conglycinin did not transform into microcapsules, but they became stable cross-linked homogeneous microgels.

pH and ionic strength responsive core-shell protein microgels fabricated via simple coacervation of soy globulins

“…The solubility of glycinin is further decreased by lowering the temperature ( Lakemond, de Jongh, Hessing, Gruppen, & Voragen, 2000;Wolf & Sly, 1967). In a recent study, Chen et al (2017b) show that the low solubility of glycinin at 0.1-0.2 M is related to the coacervation of glycinin. Initially, spherical protein rich domains are formed that with time coalesce into a continuous layer.…”

“…Simple coacervation has been observed for plant proteins, including soy glycinin (Chen, Zhao, Nicolai, & Chassenieux, 2017b), pea protein (Cochereau, Nicolai, Chassenieux, & Silva, 2019), broadbean protein (Popello, Suchkov, Grinberg, & Tolstoguzov, 1992), gliadin (Boire, Menut, Morel, & Sanchez, 2013), zein (Muthuselvi & Dhathathreyan, 2006) and kafirin (Oguntoyinbo, Taylor, & Taylor, 2018). However, compared to the complex coacervation that usually occurs between oppositely charged proteins and polysaccharides (Schmitt & Turgeon, 2011), the investigation of the simple coacervation of protein is still quite limited.…”

“…Initially, spherical protein rich domains are formed that with time coalesce into a continuous layer. Interestingly, β-conglycinin can partially inhibit the coacervation of soy glycinin (Chen et al, 2017b). Normally, depending on the type of the protein, the coacervates are destroyed upon the temperature change above or below a critical value and the turbid suspension becomes transparent at the same time (Raut & Kalonia, 2016).…”

Microgels at fluid-fluid interfaces for food and drinks

“…Producing adequate quantities of protein microgels via these methods may appear problematic, but with more research into practical processing methods this is likely be solved. Indeed, Chen et al (Chen et al, 2017b) have even shown that soy protein microgels can form 'spontaneously' from raw materials on simple changes in solution conditions. Thermally induced cross-linking can be supplemented by further chemical (Kang and Kim, 2010) or enzymatic (Guo et al, 2016) cross-linking, but this runs the risk of decreasing the acceptability of such materials in foods.…”

Functional and Engineered Colloids from Edible Materials for Emerging Applications in Designing the Food of the Future

“…In aqueous environment, both these components show peculiar behavior of globular molecules consisting of a hydrophilic shell and a hydrophobic kernel, together with a certain amount of small water‐soluble aggregates. A range of colloidal structures (microparticles, hydrogels, composite blends, fibrils, and nanoparticles) can be obtained by inducing and controlling aggregation of soy protein isolate (SPI) molecules in aqueous media by manipulating external factors such as temperature and pH or by addition of salt, desolvent, or crosslinking agents. The ligand‐binding properties of SPI make it an excellent carrier material for developing delivery systems for various hydrophobic and hydrophilic bioactive compounds.…”