Mechanistic studies on glycinin basic subunit/soybean soluble polysaccharide complexes: Ionic modulation and...

Area of Science:

• Food Science
• Biochemistry
• Colloid Science

Background:

• Soy sauce secondary precipitate contains soybean glycinin basic subunit (B) and soybean soluble polysaccharide (SSPS).
• Understanding B/SSPS complex formation is crucial for controlling soy sauce quality and enabling salt reduction.

Purpose of the Study:

• Investigate the interactions and complex formation mechanisms between B and SSPS.
• Analyze the effects of pH, B/SSPS ratio, and ionic strength on B/SSPS complex aggregation.
• Provide insights for salt reduction in soy sauce production while managing secondary precipitation.

Main Methods:

• Turbidimetry, zeta potential, particle size analysis, SEM, and structural analysis were used to study complex formation.
• Turbidimetric titration, fluorescence spectroscopy, and circular dichroism examined ion effects on aggregation.
• Systematic analysis under varying pH, B/SSPS ratios, and ion concentrations was performed.

Main Results:

• B/SSPS complex formation is primarily driven by electrostatic interactions.
• SSPS mitigates protein aggregation under acidic conditions via electrostatic repulsion and steric hindrance.
• Ion-specific effects on aggregation followed the Hofmeister series, with NaCl showing significant ionic strength dependence.

Conclusions:

• Reducing soy sauce salt content to 1.0 M appears feasible without significantly increasing precipitation risk.
• Divalent ions (MgCl₂, CaCl₂, ZnCl₂) promoted turbidity in a specific order.
• Findings offer critical data for optimizing soy sauce production, balancing salt reduction and precipitate control.