Fish Oil-Loaded Hydrogels Using a Dual Gelation Method of Fish Gelatin Cold-Setting with Ion-Alginate Cross-Linking

The development of food-grade hydrogels is an important topic for the encapsulation of bioactive substances. Herein, a dual gelation method of cold-setting with ion-alginate (ALG) cross-linking was developed to fabricate fish oil-loaded fish gelatin (FG)/ion-ALG dual hydrogels with five types of ions (H+, Ca2+, Ba2+, Fe2+, and Fe3+). The fish oil-loaded fish gelatin/ion-ALG mono hydrogels were also developed with Na+ and Mg2+. Four dual hydrogels had quicker diffusion and ion-cross-linking (H+, Ca2+, Ba2+, and Fe2+) than the FG/Fe3+-ALG dual hydrogel. All of the hydrogels showed similar water activity (0.94). The dual hydrogels had lower water contents than the mono hydrogels. Fe3+ induced the highest hydrogel hardness (28.6 ± 0.4 N) and Ba2+ induced the highest chewiness (6.3 ± 0.3 N) and gumminess (6.9 ± 0.3 N). The dual hydrogels showed lower peroxide values than the mono hydrogels. Compared with Na+, all other ions induced higher free fatty acid release percentages in the small intestinal phase. All results suggested that the cold-setting gelation and ion-ALG gelation method could be combined to prepare nutrient-loaded hydrogels. The obtained hydrogels could be applied to prepare hydrogel foods with good encapsulation of lipophilic nutrients.