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Iron deficiency is a global nutritional problem, and adding iron salts directly to food will have certain side effects on the human body. Therefore, there is growing interest in food-grade iron delivery systems. This review provides an overview of iron delivery systems, with emphasis on the controlled release of iron during gastrointestinal digestion, as well as the enhancement of iron absorption and bioavailability. Iron-bearing proteins are easily degraded by digestive enzymes and absorbed through receptor-mediated endocytosis. Instead, protein aggregates are slowly degraded in the stomach, which delays iron release and serves as a potential iron supplement. Amino acids, peptides and polysaccharides can bind iron through iron binding sites, but the formed compounds are prone to dissociation in the stomach. Moreover, peptides and polysaccharides can deliver iron by mediating the formation of ferric oxyhydroxide which is absorbed through endocytosis or bivalent transporter 1. In addition, liposomes are unstable during gastric digestion and iron is released in large quantities. Complexes formed by polysaccharides and proteins, and microcapsules formed by polysaccharides can delay the release of iron in the gastric environment and prolong iron release in the intestinal environment. This review is conducive to the development of iron functional ingredients and dietary supplements.

A novel heptapeptide LVDDHFL derived from Antarctic krill was used to assemble an iron complex, of which the iron-binding mode, in vitro digestion kinetics, and iron absorption behavior were explored. Fe 2+ bound to one carboxyl oxygen atom of Asp at position 4 and the imidazole group of His at position 5 on the LVDDHFL peptide at a stoichiometric ratio of 1:2, which induced the folding of LVDDHFL to form a more orderly structure. LVDDHFL-iron significantly enhanced the solubility of iron as compared to FeSO 4 in the gastroduodenal tract (P < 0.05), making it up to 80.92 ± 3.02% at the end of gastroduodenal digestion. Moreover, iron complexation can enhance the digestive stability of LVDDHFL with the peptide retention rate as 62.26 ± 2.60% and approximately 27.54% of LVDDHFL were degraded to hexapeptide LVDDHF. Nevertheless, the enhancement of LVDDHF - iron on iron absorption was comparable to that of LVDDHFL - iron, but better than that of FeSO 4 ., (Copyright © 2022 Elsevier Ltd. All rights reserved.)