Optimization of Goat Whey Protein-Konjac Glucomannan Hydrogel Structure and β-Galactosidase Encapsulation by Cold Plasma Pretreatment

This study investigated the structural and functional properties of composite hydrogels prepared from cold plasma (CP)-modified goat whey protein isolate (GWPI) and konjac glucomannan (KGM) for β-galactosidase (β-Gal) encapsulation. CP treatment (40 W-50 W, 10-40 s) modified GWPI structure, yielding peak surface hydrophobicity and free amino content at 50 W/40 s, which facilitated cross-linking with KGM. Composite hydrogels were fabricated under optimal CP condition (50 W/40 s) across GWPI: KGM ratios of 5:0 to 2:3. At a 4:1 GWPI:KGM ratio, the hydrogel exhibited superior network strength, mechanical properties (hardness and elasticity), water holding stability (particularly bound water retention), and crystallinity, achieving 99.36 ± 0.48% of β-Gal encapsulation efficiency and 98.57 ± 0.65% in vitro β-Gal digestion release rate. Excessive KGM content triggered phase separation, elevated free water content, and structural heterogeneity, which collectively reduced β-Gal encapsulation efficiency. These findings confirmed that synergistic modulation of CP-modified GWPI and GWPI: KGM ratios enabled simultaneous optimization of hydrogel structure, β-Gal encapsulation efficiency, and in vitro release kinetics.