On-demand, thermally triggered burst release of essential oils via native complex coacervate-stabilized emulsion gels in instant beverages.

The application of grapefruit essential oil (GEO) in acidic, high-sugar syrups is hindered by the release paradox: the need for structural confinement during storage versus rapid aroma liberation upon consumption. This study developed a marine-derived liquid encapsulation platform using fish gelatin-fucoidan complex coacervates (COA). Optimized at pH 3.3, the COA formed robust interfacial multilayers, achieving 96.1% encapsulation efficiency at 60% GEO content. Unlike conventional powders, GEO-COA maintained homogeneous dispersion and structural integrity, suppressing GEO release to <10.3% over 28 d in a real-food syrup matrix. A thermally triggered burst release is driven by a critical viscoelastic transition at 42.5 °C, where the loss of interfacial rigidity enables rapid GEO release. Consequently, dilution with 80 °C water induced 95.6% GEO release within 2 min with an immediate surge in headspace volatiles. This strategy ensures long-term storage stability in acidic syrups, while providing on-demand aroma release for instant hot-beverage applications.