Production of dialyzable iron by in vitro digestion of whey and whey components

Purpose - The purpose of this paper is to study the effect of whey and whey components on the production of dialyzable non-heme iron - an in vitro indicator of bioavailable forms of the mineral. Design/methodology/approach - Whey, processed whey and whey components were mixed with ferric iron and digested in vitro with pepsin and pancreatin/bile using a dialysis bag containing bicarbonate for pH adjustment. Total and ferrous dialyzable iron were measured and compared to values from protein and non-protein controls. Findings - Whey produced much more dialyzable iron than egg albumin but less than deproteinized whey. Most of the iron was ferric. Whey protein concentrate was as effective as egg abumin but whey protein isolate, alpha-lactalbumin and beta-lactoglobulin slightly reduced dialyzable iron formation. Milk salts produced more dialyzable iron than whey and about as much as deproteinized whey. The major component of whey producing dialyzable iron was citrate, which competes for iron chelation with the whey protein. Originality/value - This study demonstrates that whey generates a large amount of dialyzable iron from ferric iron sources and that the iron is primarily due to chelation with citrate rather than to digestion of whey proteins. However, the effect of citrate is reduced by whey proteins.