title: Effects of different proteases on iron absorption property of egg white hydrolysates.
abstract: One of the causes of iron deficiency in human is poor absorption of non-heme iron from the diet. While proteins from meats have been reported in the literature to enhance the absorption of non-heme iron, other proteins, such as those from egg, are known to inhibit iron absorption. The objective of this study is to investigate non-heme iron binding property of egg white proteins hydrolyzed using pepsin and a combination of bacterial/fungal proteases. The iron bioavailability of non-heme iron, in the presence of egg white (EW) hydrolysates, was evaluated in vitro using a tissues culture model system - rat intestinal epithelial cells (IEC-6). In the first treatment condition, EW was digested in the presence of ferrous gluconate (FeGluc), producing a peptide-FeGluc complex. In the second treatment, EW was digested in the absence of FeGluc followed by the addition of the non-heme iron. In both treatments, the resulting EW hydrolysates were further separated into >0.1-0.5kDa and >6-8kDa peptide fractions using dialysis. The hydrolysate and FeGluc complex or mixtures were applied to the IEC-6 cells and iron absorption was measured after 2h or 16h. Results showed that the peptide-FeGluc complex digested with a combined proteases from Bacillus licheniformis (SDAY) and from Aspergillus melluss (PP) increased the in vitro iron-binding property but did not enhance iron uptake by the in IEC-6 cells (p<0.05). Peptide-FeGluc complex digested with pepsin alone (>0.1-0.5kDa) resulted in significantly higher iron uptake in IEC-6 cells compared with the higher molecular weight complex (>6-8kDa) produced using the same hydrolysis treatment. Similarly, enhanced iron uptake was observed with the complexes produced with the combined SDAY and PP enzymatic treatments (>0.1-0.5kDa and >6-8kDa) (p<0.05). On the other hand, the enhanced iron absorption effect was not observed when pre-hydrolyzed free peptides were added to FeGluc. Overall, this study suggests that low molecular weight fractions of egg white protein hydrolysates can enhance the bioavailability of non-heme iron. Furthermore, the method by which the egg white proteins are being prepared, i.e., in the presence or absence of FeGluc, can affect the bioavailability of the non-heme iron.
authors.affiliation: Department of Food Science, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
authors.forename: Yasumi
authors.initials: Y
authors.lastname: Horimoto
authors.affiliation: Department of Food Science, University of Guelph, Guelph, Ontario N1G 2W1, Canada. Electronic address: llim@uoguelph.ca.
authors.forename: Loong-Tak
authors.initials: LT
authors.lastname: Lim
mesh_terms: D000818:Animals; D001682:Biological Availability; D002460:Cell Line; D004527:Egg Proteins / Q000737:chemistry*; D005296:Ferrous Compounds / Q000737:chemistry; D006868:Hydrolysis; D007408:Intestinal Absorption; D007501:Iron / Q000493:pharmacokinetics*; D008970:Molecular Weight; D010434:Pepsin A / Q000737:chemistry; D010447:Peptide Hydrolases / Q000737:chemistry*; D011492:Protein Hydrolysates / Q000737:chemistry*; D051381:Rats
chemical_list: D004527:Egg Proteins; D005296:Ferrous Compounds; D011492:Protein Hydrolysates; D007501:Iron; D010447:Peptide Hydrolases; D010434:Pepsin A; C011819:ferrous gluconate
keywords: Egg white peptides; Food proteins; Hydrolysis; IEC-6 cells; Iron absorption; Iron bioavailability