Milk protein-iron complexes: Inhibition of lipid oxidation in an emulsion

Abstract

-Fortification of foods with iron is a common vehicle for delivering iron in required quantities to the consumer. However, many technological problems occur when food products are fortified with minerals, due mainly to the many reactions of minerals with other food components, e.g. fat oxidation. In the present study, the binding of iron (ferrous sulphate) to common milk protein products, sodium caseinate, whey protein isolate (WPI) and milk protein concentrate (MPC), to form protein-iron complexes was characterized by the amount of iron binding and the turbidity as functions of the iron concentration. In an emulsion containing linoleic acid, the oxidation activity of these protein-iron complexes was compared with that of the iron in its free state. The affinities of caseinate and MPC to bind iron were higher than that of WPI. These differences were attributed to the presence of clusters of phosphoserine residues in casein molecules, that are known to bind divalent cations strongly. Lipid oxidation experiments showed that the ability of iron to catalyse lipid oxidation was reduced significantly when iron was bound to protein compared with when it was in its free form. This suggests that the formation of milk protein-iron complexes could be a novel way of incorporating iron into food products with high bioavailability, good flavour and no solubility problems. sodium caseinate / whey protein isolate / milk protein concentrate / protein-iron complex / emulsion oxidationRésumé -Complexes protéines laitières-fer : inhibition de l'oxydation des lipides dans une émulsion. La fortification en fer des aliments est utilisée couramment pour apporter aux consommateurs les quantités nécessaires en fer. Cependant, beaucoup de problèmes technologiques surviennent quand les produits alimentaires sont fortifiés avec des minéraux, principalement en raison de nombreuses réactions des minéraux avec les autres composants des aliments, par exemple Article published by EDP Sciences l'oxydation de la matière grasse. Dans la présente étude, la liaison du fer (sulfate de fer) à des produits protéiques laitiers courants, caséinate de sodium, isolat de protéines de lactosérum et concentré de protéines laitières, pour former des complexes protéines-fer a été caractérisée par la quantité de fer lié et la turbidité en fonction de la concentration en fer. Dans une émulsion contenant de l'acide linoléique, l'activité oxydante de ces complexes protéines-fer a été comparée avec l'activité oxydante du fer à l'état libre. Les affinités du caséinate et du concentré de protéines laitières pour lier le fer étaient plus élevées que celle de l'isolat de protéines de lactosérum. Ces différences ont été attribuées à la présence dans les molécules de caséine d'amas de résidus phosphosérine qui sont connus pour lier fortement les cations divalents. Les essais d'oxydation des lipides ont montré que la capacité du fer à catalyser l'oxydation des lipides était significativement réduite quand le fer était lié aux protéines par rapport à celle obtenue q...

Iron binding to caseins in the presence of orthophosphate

“…However, substantial precipitation of iron occurred in the solution containing P10 mM ferric chloride (Fig. 1A) and sodium caseinate, in agreement with previous work (Gaucheron et al, 1996;Sugiarto, Ye, Taylor, & Singh, 2010). At these concentrations of iron, sodium caseinate also showed extensive precipitation (Fig.…”

Effects of mineral content of bovine drinking water: Does iron content affect milk quality?

“…Lactoferrin and transferrin may prevent the interaction of minerals with milk lipids (Allen and Hamilton, 1994). If iron fortification can be carried out such that the iron binds to the proteins, the oxidation process slows by a significant degree (Sugiarto et al, 2010;GuzunCojocaru et al, 2011).…”

“…Elevated levels of iron in the water given to cattle could have a potential effect on milk synthesis, too. Though it is known that iron acts as a prooxidant, little research has been identified that examines the specific role of iron in the water given to dairy cattle (Sugiarto et al, 2010). It is known that iron can affect palatability of the water provided to cattle, which may cause the animals to consume less water, leading to less milk production (National Primary Drinking Water Regulations, 2011).…”

Impact of protein pre-treatment conditions on the iron encapsulation efficiency of whey protein cold-set gel particles

“…One of the micronutrients of interest for fortiWcation to food is iron, as iron deWciency is one of the most prevalent nutritional deWciencies in the world. Given that the presence of amino acids in the intestines is required to increase iron bio-availability [10], the use of protein gels oVers an interesting alternative for protecting iron against oxidation [11], increasing dietary iron adsorption [12] and oVering masking of oV-Xavours.…”