Gelation Mechanisms and Properties of Soy Protein Systems

Soy proteins, principally β-conglycinin (7S) and glycinin (11S), undergo denaturation and association under controlled conditions of heat, pH, ionic strength and enzymatic or acidifying agents to form three-dimensional gel networks. Unfolding of globular subunits exposes hydrophobic patches and free sulfhydryl groups, which drive aggregation through hydrophobic interactions and disulfide bond rearrangement. Acid-induced gelation utilises gradual pH reduction to near the isoelectric point, minimising electrostatic repulsion and promoting network formation, while salt-induced gelation screens charges and enhances ionic cross-linking. Thermal gelation, often combined with transglutaminase or polysaccharide co-gelling agents, further stabilises the network and modulates texture. Resulting gels exhibit tunable water-holding capacity, firmness and elasticity, critical for tofu, meat analogues and dairy alternatives. Microstructural control—via processing steps such as spray drying, ion addition and pretreatment—determines pore size, homogeneity and sensory attributes. Advances in understanding the balance of non-covalent and covalent interactions have enabled the design of soy protein systems with targeted rheological properties and improved stability under varying storage and processing conditions.

Research from Nature Portfolio

Recent studies have elucidated the molecular pathways by which acidifiers and divalent ions govern soy protein gelation. Investigation into glucono-δ-lactone (GDL)-induced aggregation revealed that slow pH decline fosters formation of 7S- and 11S-isoflavone complexes, which precipitate into a cohesive gel matrix upon reaching pH ≈ 5.5. Detailed electrophoretic and chromatographic analyses demonstrated co-precipitation of aglycone isoflavones with protein subunits, highlighting the role of protein–polyphenol interactions in gel stability. Complementary work on calcium chloride-mediated coagulation showed that millimolar concentrations of Ca²⁺ promote extensive cross-linking of glycinin and β-conglycinin, together with bound isoflavones, yielding gels with enhanced hardness and reduced syneresis. These findings collectively improve mechanistic insight into ion-specific modulation of network formation and guide formulation strategies for tailored textural outcomes.

Gelation Mechanisms and Properties of Soy Protein Systems publication trend

The graph below shows the total number of articles in gelation mechanisms and properties of soy protein systems across all publications each year (not limited to Nature Index journals).

Technical terms

β-conglycinin (7S): Trimeric soy protein fraction comprising α, α′ and β subunits, influential in gel network formation.

Glycinin (11S): Hexameric storage protein in soy, consisting of acidic and basic polypeptides linked by disulfide bonds.

Hydrophobic interactions: Associations between non-polar amino acid residues driving protein aggregation.

Disulfide bonds: Covalent links between cysteine side chains stabilising protein tertiary and quaternary structure.

Glucono-δ-lactone (GDL): Slow-release acidulant that lowers pH to induce isoelectric precipitation of soy proteins.

Isoflavones: Phenolic compounds in soy that can bind to protein subunits and influence gelation behaviour.

Rheology: Study of the deformation and flow properties of gels, including viscoelastic parameters.

References

1. Aggregation of soy protein-isoflavone complexes and gel formation induced by glucono-δ-lactone in soymilk. Scientific Reports (2016).
2. Coagulation of β-conglycinin, glycinin and isoflavones induced by calcium chloride in soymilk. Scientific Reports (2015).
3. Changes of Soybean Protein during Tofu Processing. Foods (2021).
4. Effect of Oxidation on Quality of Chiba Tofu Produced by Soy Isolate Protein When Subjected to Storage. Foods (2020).
5. Addition of Salt Ions before Spraying Improves Heat- and Cold-Induced Gel Properties of Soy Protein Isolate (SPI). Applied Sciences (2019).