Effects of pressure-resistant bilayer microcapsules and ultra-high pressure on gel stability and nutrient retention of high-oil surimi gels.

Thermal processing of yellowfin tuna (Thunnus albacares) often results in lipid oxidation and textural degradation, particularly in high-oil formulations. In this study, a pressure-resistant "rigid-elastic" bilayer microcapsule (gelatin: κ-carrageenan: carboxymethyl chitosan = 3: 1: 1, onset thermal degradation temperature = 395 °C) was developed and combined with ultra-high pressure (UHP, 300 MPa) to improve the stability of fish oil-enriched surimi gels. The microcapsules maintained morphology integrity after UHP treatment, exhibiting a low fracture rate of 0.6%, which enabled effective physical confinement of fish oil within the pressure-restructured surimi gel matrix. The microcapsule-UHP coupling promoted protein unfolding and subsequent intermolecular cross-linking, reducing the dehydration and de-oiling rates of the surimi products by 62.4% and 58.7%, respectively, while increasing gel strength by 75.2%. Concurrently, lipoxygenase activity and free radical generation decreased by 47.6% and 79.8%, respectively, effectively delaying lipid oxidation and protecting EPA and DHA. These results indicate that pressure-tolerant encapsulation can improve oil retention by reinforcing matrix confinement during gelation, thereby providing an effective strategy for producing nutritionally fortified and process-stable seafood gel systems.