Effect of oil phase volume fraction on curcumin-loaded Pickering emulsions stabilized by soy protein isolate/sodium alginate complex particles: Stability and in vitro digestibility

To enhance both the stability and bioaccessibility of curcumin, curcumin-loaded Pickering emulsions were fabricated using soy protein isolate/sodium alginate complex particles as stabilizers. The effect of oil phase volume fraction on emulsion properties was examined, along with the potential of high internal phase Pickering emulsions (HIPPEs) for stabilized curcumin delivery. The structural characteristics of the emulsions were systematically studied by measuring droplet size distribution, microstructure, and rheological behavior. Meanwhile, their antioxidant activity, stability, and the bioaccessibility of the encapsulated curcumin were evaluated. Among the tested formulations, an oil phase volume fraction of 75% exhibited optimal properties. Rheological measurements further confirmed that this specific oil phase volume fraction formed the strongest viscoelastic gel network, which was crucial for maintaining emulsion structural stability. Encapsulation of curcumin within high internal phase Pickering emulsions greatly enhanced its stability and bioaccessibility. In particular, when the oil phase volume fraction was set at 75%, the bioaccessibility of curcumin reached its highest value of 42.34%. Taken together, this work offers useful guidance for broadening the use of soy protein isolate–sodium alginate complex nanoparticles in food delivery systems.