Abstract: In this study, W1/O/W2 double emulsion gels were prepared by a three-step method using low-acyl gellan gum (LA) as a substrate, and the effect of LA concentration on the microstructure, particle size, water-holding capacity, rheology, stability and encapsulation efficiency of the double emulsion gel were investigated, aiming to develop a suitable double emulsion gel system for the co-delivery of oyster peptides and curcumin. The results showed that the particle size of the double emulsion gel gradually decreased and the water-holding capacity significantly increased as the concentration of gellan gum increased. Correspondingly, the storage modulus (G’) and apparent viscosity rose, accompanied by a continuous improvement in the encapsulation efficiency. At LA concentrations not lower than 0.4%, the emulsion gels displayed particle sizes < 7.00 μm and water-holding capacity exceeding 80% and formed distinct network structures. The encapsulation efficiencies for oyster peptides and curcumin were 67.36% and 74.99% at LA concentrations of 0.4% and 0.5%, respectively. Furthermore, a noticeable reduction in the off-odor of oyster peptides was observed. The addition of LA significantly enhanced the stability of the double emulsion gel, effectively protecting oyster peptide and curcumin. This was demonstrated by the following observations: 1) the double emulsion gel showed no phase separation after 28 days of storage at 4 ℃ and remained stable with limited changes in particle size following heat treatment at 90 ℃; 2) although slight droplet coalescence occurred after three freeze-thaw cycles, the double emulsion’s structure remained intact; 3) after ambient storage (at 25 ℃ for 7 or 14 days), heat treatment (at 90 or 70 ℃ for 30 min), and three freeze-thaw cycles, the double emulsion gel exhibited retention rates of 86.13%–97.86% and 89.19%–95.94% for encapsulated oyster peptides and curcumin, respectively. In vitro simulated gastrointestinal release study demonstrated that the double emulsion gel prepared with 0.4% LA exhibited controlled release characteristics for both oyster peptides and curcumin. After 24 h dialysis in simulated gastric fluid, the cumulative release rates of oyster peptides and curcumin were 23.97% and 22.17%, respectively. Following subsequent 24 h dialysis in simulated intestinal environment, the release rates significantly increased to 34.7% and 47.52%, respectively. This study provides a novel strategy for the co-delivery of oyster peptides and curcumin.

Key words: oyster peptides; curcumin; double emulsion gel; stability; low-acyl gellan gum