This study is aimed at designing of a composite cold-set hydrogel using whey protein isolate (WPI) and gellan gum as iron carrier. The effect of total polymer concentration (TPC) (0.5 and 1.5%), WPI/gellan ratio (1:1, 1:2, and 1:3), and iron concentration (10, 40, and 70 mM) on physicochemical and rheological characteristics of hydrogel were analyzed. By increasing TPC, the release mechanism became complex regarding less erosion of structure in simulated gastrointestinal medium. Moreover, the C–– O peak area of FTIR spectra was enhanced. As WPI/gellan ratio decreased, the faster release occurred due to a more porous structure. The cumulative release of iron in acidic and neutral pH increased up to 71.74 and 9.14%; however, iron was released up to 88.55 and 28.72% in simulated gastric and intestinal medium, respectively. The iron release followed a chemicallycontrolled mechanism in all samples. The area and number of gel pores and water-holding capacity decreased as Fe concentration was enhanced, but denaturation temperature increased. These results suggest that the strong texture with a solid elastic behavior along with a high cumulative release of iron made our hydrogel suitable for iron delivery to reduce iron deficiency-related disorders.

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