Micellar Casein-Based Emulsion Gels: Characteristics and Property Regulation by Pectin/Chitosan Oligosaccharide

Emulsion gels are widely used in the food industry, yet precise control of their gelation and structural characteristics remains challenging. Micellar casein (MC) forms emulsion gels via shear-induced jamming transition, whereas its critical gelation rules and intermolecular mechanisms are unclear. This work established jamming gelation criteria for MC-based emulsion gels. Emulsion gels were fabricated by one-step homogenization at oil fractions of 0.65-0.75 with 1%-8% MC; stronger shear was needed at lower oil fractions. Gel-like structures formed across various MC concentrations, yet long-term stability strongly depended on concentration, and 5%-6% MC yielded uniform jammed droplet networks with optimal storage stability. Subsequently, negatively charged pectin (P) and positively charged chitosan oligosaccharide (CO) were utilized to tailor gel properties through opposite electrostatic interactions. Two preparation routes for emulsion gels were adopted: one-step homogenization after premixing P/CO with MC, and two-step homogenization where P/CO was incorporated into pre-formed MC-based gels. Both polysaccharides greatly enhanced the storage, pH and thermal stability of 4% MC gels, extending shelf life beyond 240 days. P-MC systems relied mainly on electrostatic repulsion and synergistic hydrogen bonding, whereas CO-MC gels were dominated by electrostatic attraction to thicken interfacial films and raise viscoelasticity. The one-step method suited MC-only and P-MC emulsion gels, whereas two-step preparation optimized CO-MC gel's microstructure and rheology. This study elucidates MC jamming gelation thresholds and two oppositely charged polysaccharides modulation mechanisms, offering references for designing high-performance food-grade emulsion gels. PRACTICAL APPLICATIONS: The established jamming gelation criteria and electrostatic modulation by pectin or chitosan oligosaccharide can guide scalable production of micellar casein emulsion gels in food manufacturing. Selective use of the two polysaccharides together with matched preparation procedures enables tailored gel microstructure, rheology and environmental stability. This research provides feasible technical strategies for the development of high-stability and performance-tunable emulsion gels.