Response surface methodology-guided design of oil-in-water emulsions coated with complex coacervates for precision intestinal delivery of sulforaphane.

Sulforaphane (SFN) is structurally unstable and sensitive to pH variations. This study developed O/W emulsions coated with complex coacervate (ECC) composed of mung bean protein isolate (MPI) and ι-carrageenan. The SFN-loaded ECC (SFN-ECC) was fabricated to enhance stability and targeted delivery. A two-stage response surface methodology was applied to sequentially optimize the formulation, targeting emulsion stability and size first, then coacervate coating yield and encapsulation efficiency. The optimal parameters were identified as 8793 rpm, 54% oil, 0.6% ι-carrageenan, 1.17% MPI, and pH 3.71. The resulting SFN-ECC exhibited a compact core-shell morphology and improved thermal stability due to strong protein-polysaccharide interactions. In vitro digestion models demonstrated that SFN-ECC minimized gastric release to 6.9% while enhancing controlled intestinal delivery to 45.1%. This dual-layer encapsulation suppresses premature release under gastric conditions and enables controlled release at the intestinal stage, offering a strategy to improve the bioavailability of unstable lipophilic bioactives in functional foods.