Whey protein-iron or zinc complexation decreases pro-oxidant activity of iron and increases iron and zinc bioavailability

Effect of different iron ratios on interaction and thermodynamic stability of bound whey protein isolate

Whey protein isolates (WPI) are known to have mineral-binding capacity to promote iron absorption. The aim of this study was to investigate the effect of iron ratio on the conformational structure of iron-bound whey protein isolate (WPI-Fe) and its thermodynamic stability. It was shown that the iron to protein ratio affects both the iron binding capacity of WPI and the iron valence state on the surface of WPI-Fe complexes. As the iron content increases, aggregation between protein molecules occurs. In addition, WPI-Fe nanoparticles have thermodynamic stability and Fe2+ has a high affinity with WPI for spontaneous exothermic reactions. This study demonstrates that WPI-Fe complexes can be used to efficiently deliver high-quality iron source (Fe2+) for future iron supplements.

Recent advances in iron encapsulation and its application in food fortification

Iron (Fe) is an important element for our body since it takes part in a huge variety of metabolic processes. However, the direct incorporation of Fe into food fortification causes a number of problems along with undesirable organoleptic properties. Thus, encapsulation has been suggested to alleviate this problem. This study first sheds more light on the Fe encapsulation strategies and comprehensively explains the results of Fe encapsulation studies in the last decade. Then, the latest attempts to use Fe (in free or encapsulated forms) to fortify foods such as bakery products, dairy products, rice, lipid-containing foods, salt, fruit/vegetable-based products, and infant formula are presented. Double emulsions are highly effective at keeping their Fe content and display encapsulation efficiency (EE) > 88% although it decreases upon storage. The encapsulation by gel beads possesses several advantages including high EE, as well as reduced and great Fe release in gastric and duodenal conditions, respectively. Cereals, particularly bread and wheat, are common staple foods globally; they are very suitable for food fortification by Fe derivatives. Nevertheless, the majority of Fe in flour is available as salts of phytic acid (IP6) and phytates, reducing Fe bioavailability in the human body. The sourdough process degrades IP6 completely while Chorleywood Bread Making Process and conventional processes decrease it by 75% in comparison with whole meal flour.

Preparation of whey based savory beverage with enhanced bio-accessible zinc

Zinc is an essential micronutrient for numerous catalytic, structural and regulatory functions in human body. However, its direct fortification in the food matrix poses the challenges of decreased bio-accessibility by forming insoluble sediments. Complexing zinc with polysaccharides has been reported as a possible intervention to address this issue by keeping the zinc in soluble form. Present investigation was undertaken to transform paneer whey containing complexed zinc into a sensorially acceptable beverage by varying its pH from 3.5 to 5.5, common salt concentration from 0.5 to 1.5% and spices concentration at 0.2 and 0.4%. Changes in complexed zinc concentration, apparent viscosity, instrumental color parameters and sensory attributes were determined. Complexed zinc concentration increased (p < 0.05) with increasing pH, decreasing salt and increasing spices concentration. Whey beverage having 4.5 pH, 1.0% salt and 0.4% spices concentration was most preferred by the sensory panelists. In-vitro digestion of optimized whey beverage revealed that bio-accessibility of zinc was significantly higher (p < 0.05) in complex form than free from.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-022-05497-y.

Iron Absorption: Factors, Limitations, and Improvement Methods

Iron is an essential element for human life since it participates in many functions in the human body, including oxygen transport, immunity, cell division and differentiation, and energy metabolism. Iron homeostasis is mainly controlled by intestinal absorption because iron does not have active excretory mechanisms for humans. Thus, efficient intestinal iron bioavailability is essential to reduce the risk of iron deficiency anemia. There are two forms of iron, heme and nonheme, found in foods. The average daily dietary iron intake is 10 to 15 mg in humans since only 1 to 2 mg is absorbed through the intestinal system. Nutrient-nutrient interactions may play a role in dietary intestinal iron absorption. Dietary inhibitors such as calcium, phytates, polyphenols and enhancers such as ascorbic acid and proteins mainly influence iron bioavailability. Numerous studies have been carried out for years to enhance iron bioavailability and combat iron deficiency. In addition to traditional methods, innovative techniques are being developed day by day to enhance iron bioavailability. This review will provide information about iron bioavailability, factors affecting absorption, iron deficiency, and recent studies on improving iron bioavailability.

Iron delivery systems for controlled release of iron and enhancement of iron absorption and bioavailability

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.

Synthesis and physicochemical characterization of zinc-lactoferrin complexes

One trend of the modern world is the search for new biologically active substances based on renewable resources. Milk proteins can be a solution for such purposes as they have been known for a long time as compounds that can be used for the manufacturing of multiple food and non-food products. Thus, the goal of the work was to investigate the parameters of Zn-bovine lactoferrin (bLTF) interactions, which enables the synthesis of Zn-rich protein complexes. Zinc-bLTF complexes can be used as food additives or wound-healing agents. Methodology of the study included bLTF characterization by sodium dodecyl sulfate-PAGE, MALDI-TOF, and MALDI-TOF/TOF mass spectrometry as well Zn-bLTF interactions by attenuated total reflection-Fourier-transform infrared, Raman spectroscopy, scanning and transmission microscopy, and zeta potential measurements. The obtained results revealed that the factors that affect Zn-bLTF interactions most significantly were found to be pH and ionic strength of the solution and, in particular, the concentration of Zn²⁺. These findings imply that these factors should be considered when aiming at the synthesis of Zn-bLTF metallocomplexes.

Polyphosphates as an effective vehicle for delivery of bioavailable nanoparticulate iron(III)

Polyphosphates are widely used food additives with the potential to increase iron bioavailability but chemical nature of their soluble complexes with iron remains largely unknown. Here, pyrophosphate, tripolyphosphate, hexametaphosphate and ∼25-chain-length polyphosphate solubilized 896, 896, 1120 and 1344 mg Fe(III) per g, respectively, at neutral pH by mediating the formation of highly-negatively-charged ferric hydroxide-polyphosphate nanoparticles (PolyP-FeONPs). PolyP-FeONPs displayed fading yellow color with increasing initial dissolved P/Fe ratio ((P/Fe)_init) and decreasing polyphosphate length due to rising proportion of Fe(III)-phosphate bonds, and specifically, pyrophosphate resulted colorless PolyP-FeONPs at (P/Fe)_init ≥ 4. PolyP-FeONPs had weak pro-oxidant activity in glyceryl trilinoleate emulsion and good colloidal stability under spray/freeze-drying and gastrointestinal conditions. Serum iron kinetics in rats revealed sustained iron release and ∼170% iron bioavailability of oral PolyP-FeONPs relative to FeSO₄. Calcein-fluorescence-quenching assay in polarized Caco-2 cells unveiled divalent-metal-transporter-1-independent and macropinocytosis-dependent iron uptake from PolyP-FeONPs. This study helps develop food-compatible, highly-bioavailable and sustained-release iron preparations.