Structural and chemical insights into egg yolk granule-chitosan complex system: How pH-modulation improve functional properties.

Egg yolk granules (EYGs) are nutrient-rich by-products of immunoglobulin extraction with a dense structure that limits their applications in food systems. Chitosan (CS) was utilized to regulate the physicochemical characteristics and the effects of varying EYGs-CS ratios and pH values were studied. The formation mechanism, microstructures, interfacial properties, and emulsification properties were systematically investigated. FTIR and XRD results confirmed electrostatic interactions and hydrogen bonding as the driving forces. This complexation disrupted the calcium- phosphate bridges in EYGs, as evidenced by a lower denaturation temperature and enhanced water mobility, creating a more flexible amphiphilic structure. The flexible complex significantly improved interfacial properties, achieving a contact angle near 90° and reducing interfacial tension. Consequently, superior emulsification properties were achieved at an optimal EYGs-CS ratio of 2:1 under acidic conditions (pH 3.0-5.0). This study demonstrates that pH-responsive EYGs-CS complex system can enhance functional properties by modulating microstructure and interfacial characteristics.