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

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.