Protein-based hydrogels and emulgels are soft solids of particular interest in designing functional foods due to their ability to retain water or emulsified lipid droplets within the gel matrix. They can act as fat substitutes or mimetics, providing healthier food products. Thus, much research has been conducted to evaluate the influence of different factors on water holding, color changes, lipid oxidation, and textural and fracture properties of edible gels derived from proteins (Hou et al., 2022; Iwaki, Aono, Hayakawa, Fu, & Otobe, 2020; Koç et al., 2019; Lam & Ikeda, 2017; Wu et al., 2019; Ren et al., 2022), showing the suitability of the structured systems in the reformulation of food matrixes.

In this context, bovine blood from slaughterhouses can be easily collected and processed to obtain protein fractions that deliver specific functionality to various food products. This functionality includes relevant technological properties such as emulsifying and gelling capacity, which has motivated the use of blood-derived products as valuable ingredients, either by the food industry or as dietary supplements (Andago, Imungi, Mwangi, Lamuka, & Nduati, 2015; Lynch, Mullen, O'Neill, Drummond, & Álvarez, 2018). The studies mainly focused on the techno-functionality of bovine blood plasma (BBP) due to its lack of problems concerning developing undesirable flavors or colors (Baracco, Rodriguez Furlán, & Campderrós, 2017; Fernández, Romero, Rolhaiser, Fogar, & Doval, 2021; Rodriguez Furlán, Padilla, & Campderrós, 2014). Contrary, only a few considered the techno-functionality or the nutritional value of the red cells fraction (RFC) mainly due to the dark color that it imparts (Toldrá, Lynch, Couture, & Álvarez, 2018; Tang, Zhu, & Zhuang, 2015).

RFC is rarely used in elaborating human food products despite its high heme‑iron content. Thus, one strategy for taking advantage of its nutritional value might be the combined use with BBP, in agreement with many other studies that reported the combined use of substances to enhance the properties of the resulting gels. For example, gellan gum has been used to modulate the technological functionality of egg white heat-induced hydrogels for designing food formulations with anti-obesity properties (Babaei, Khodaiyan, & Mohammadian, 2019). Also, Chen, Gan, Ji, Song, and Yin (2019) evaluated the properties of combined corn fiber gum-soy protein isolate to produce double-network hydrogel-based food products with various texture profiles. Similarly, Paglarini, Vidal, Martini, Cunha and Pollonio (2022) used EGs from soybean oil and soy protein isolate combined with carrageenan, chia flour, and inulin as a fat replacer in Bologna sausage with an enhanced fatty acid profile.

On the other hand, the ability of proteins to develop consistent micronutrient delivery systems has been proven. Prichapan, McClements, and Klinkesorn (2018) used o/w emulsions to incorporate iron, although the interactions between the micronutrient and other components were the main drawback. Thus, much research evaluated the potential use of immobilized iron in three-dimensional networks as delivery systems, making retention efficiency the suitable primary indicator (Kazemi-Taskooh & Varidi, 2021; Martins, Bourbon, Pinheiro, Fasolin, & Vicente, 2018; Naktinienė, Eisinaitė, Keršienė, Jasutienė, & Leskauskaitė, 2021).

Despite the high interest of food research in developing functional ingredients, bifunctional ingredients seem an attractive option nowadays. Rice flour emulgel (Oppong, Panpipat, Cheong, & Chaijan, 2022) and bifunctional polyphenolic coating (Goulas et al., 2019) are examples of food applications. Thus, this study aimed to harness the functionality of bovine blood plasma and the nutritional value of the red cells fraction to develop bifunctional gels with potential use in the production of heme iron-enriched food products with reduced fat content or improved lipid profile.