Iron Complexes With Proteins, Carbohydrates, and Maillard Products in Dairy Systems: Implication for Fortification, Bioavailability, and Product Functionality.

The global prevalence of iron (Fe) deficiency anemia (IDA) continues to pose major public health challenges, necessitating the development of effective fortification strategies. Dairy-based systems are promising vehicles for Fe fortification and delivery due to their widespread consumption and nutritional value, although their complex matrix presents significant challenges for maintaining Fe bioavailability and product quality. This review critically evaluates current knowledge on Fe fortification in dairy systems, integrating evidence on Fe forms, physicochemical interactions between Fe and the matrix, and their consequent effects on Fe bioavailability and physical functionality. Emerging fortification strategies are highlighted. Conventional Fe salts, including ferrous sulfate, ferrous fumarate, and ferric pyrophosphate, have varying degrees of solubility and absorption but are often associated with adverse sensory changes, lipid oxidation, and reduced product stability. Fe-ligand complexes, including protein-, carbohydrate-, and Maillard reaction product (MRP)-based systems, can impart improved stability to the fortified product and bioavailability by minimizing interactions with inhibitors of Fe absorption. The incorporation of Fe into dairy matrices influences product pH and structural and functional properties while also accelerating lipid oxidation and sensory deterioration when inorganic salts are used. Strategies such as Fe chelation, microencapsulation, and co-fortification with enhancers have shown potential to mitigate these limitations. In addition, the role of prebiotics, probiotics, and MRPs in modulating Fe absorption remains complex and context dependent. Despite promising advancements, gaps remain in understanding interactions between Fe, proteins, carbohydrates and MRP and their implications for Fe fortification of dairy systems. Future research should focus on developing integrated fortification approaches enabling the design of next-generation functional dairy foods to effectively combat global Fe deficiency.