Abstract
Protein hydrophobic interaction has been considered the most important factor dominating protein folding, aggregation, gelling, self‐assembly, adhesion, and cohesion properties. In this paper, morphology and phase separation of hydrophobic clusters, networks, and aggregates of soy globular protein polymers, induced by using a reducing agent (NaHSO~3~), are studied using microscopic instruments. The morphology and phase separation of these hydrophobic clusters are sensitive to protein structure and composition, pH, and ionic‐strength (I~m~). Most of the clusters are in spherical‐shape architecture and mainly consist of hydrophobic polypeptides. Rod‐shape clusters were also observed at higher ionic strength, and mainly consist of hydrophilic polypeptides. The ratio of hydrophobic/hydrophilic (HB/HL) polypeptides is important to facilitate the formation of clusters in an environment with a certain pH value and ionic strength. At HB/HL 0.8, uniform spherical clusters were observed and diameters ranged from 30 to 70 nm. At HB/HL <0.8, large spherical clusters were formed with diameters ranging from 100 to 1 000 nm, and at HB/HL ≥1.8, large hydrophobic aggregates formed, and size of aggregates can be up to 2 500 nm. When solid content increased from 3% to 38%, at I~m~ ≤ 0.058 mol · L^−1^, pH = 4.8, HB/HL ratio <0.8, the networks turned into a continuous substance that has strong adhesion to various surfaces; at I~m~ ≥ 0.115 mol · L^−1^, HB/HL ratio ≥1.8, the large aggregates became very cohesive and viscoelastic. Clear phase separation was observed during curing between hydrophobic and hydrophilic protein polymers. Phase‐separation degree increased as HB/HL ratio increased.
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