Formulation of Emulsion Gels Stabilized by Soy Protein Isolate and Gellan Gum Conjugates for 3D Printing and β-Carotene Encapsulation Applications

Abstract

Soy protein isolate–gellan gum (SPI–GG) conjugates were prepared at different mass ratios to investigate how protein–polysaccharide composition affects the physicochemical, emulsion, rheological, and functional properties of CEGs. Increasing the GG proportion enhanced the degree of glycation and Maillard browning while producing opposite trends in solubility and surface hydrophobicity. All SPI–GG CEGs exhibited smaller droplets, more negative ζ-potential values, and higher emulsifying activity and stability than the SPI control. Among the formulations, S1G1 showed the smallest and most uniformly distributed droplets, the highest emulsifying performance, and the greatest β-carotene encapsulation efficiency (90.94 ± 0.55%) and bioaccessibility (68%). In contrast, rheological and printing performance showed a different composition-dependent response. All CEGs exhibited shear-thinning behavior, solid-like viscoelasticity, and thixotropic recovery above 70%. CEG-S1G1.5 exhibited a combination of relatively high G*, critical strain, and yield stress, together with favorable dimensional retention after printing. These findings demonstrate that the SPI–GG ratio differentially affects emulsion characteristics and bulk rheological properties. Overall, the SPI–GG composition associated with favorable functional performance differed according to the intended application, providing a basis for composition-driven design of CEGs for 3D printing and lipophilic bioactive delivery.