Synergistic effects of ultrasound pretreatment and λ-carrageenan complexation on the stability and quercetin delivery efficiency of tilapia protein emulsion gels: The role of λ-carrageenan concentration.

The application of quercetin in functional foods is severely limited by its poor aqueous solubility, chemical instability, and low oral bioaccessibility. This study investigated the synergistic effects of ultrasound pretreatment and λ-carrageenan (λ-CA) complexation on the stability and quercetin delivery efficiency of tilapia protein (TP)-based emulsion gels. The results showed that ultrasonication induced partial unfolding of the TP secondary structure and tertiary conformation, thereby exposing more hydrophobic groups and free sulfhydryl groups, which promoted the formation of UTP-λ-CA complexes with enhanced solubility. More importantly, this synergistic strategy constructed a denser, more ordered gel network, providing effective steric hindrance against droplet aggregation and significantly enhancing the viscoelasticity, environmental stability, and digestive resistance of the system. Compared with UTP-0.1%λ-CA and UTP-0.2%λ-CA complex-stabilized emulsion gels, the UTP-0.3%λ-CA emulsion gel exhibited the smallest droplet size (D4,3 = 14.95 μm, D3,2 = 2.80 μm), the highest storage modulus (G'), and superior viscoelasticity. It also demonstrated the highest quercetin retention rates after UV irradiation (77.07%) and thermal treatment (74.93%). Furthermore, this system achieved the greatest quercetin bioaccessibility (31.19%), a 2.09-fold increase compared to the TP emulsion gel (14.92%). These findings provide theoretical support for the development of high-performance aquatic protein-based delivery systems for hydrophobic bioactive compounds.