Extraction Of Collagen From Alaska Pollock Skin And Iron Absorption Promoting Effect Of The Small Collagen Peptides

Iron(Fe)is an essential micronutrient for the growth and health of human.Organisms iron is an excellent iron supplement due to its bioavailability.Both amino acids and peptides improve iron bioavailability or promote iron absorption.Then they are promising iron supplements.Amino acids and small peptides are promising iron absorption promoter for their easy-absorption properties.Alaska Pollock(Theragra chalcogramma)is rich in resource.And during its processing,collagen-rich skin is peeled as byproducts.In this article we extracted collagen from the Alaska Pollock and hydrolysated the collagen by collagenase,and then studied the iron biding ability of collagen small peptides(amino acids),and the complexes shown a good iron absorption promote effect on the Caco-2 cell.This study proved that Alaska Pollock skin could be the high added-value product.Three kinds of collagens were extracted by using acid,pepsin-assisted acid or hot water.The productivity of acid soluble collagen(ASC),pepsin soluble collagen(PSC)and hot water soluble collagen(WSC)were 7.33%,12.67%and 30.89%respectively.Their purity and character were similar and then the hot water extraction is the best way to extract collagen.Through response surface method,the optimum extraction conditions of extracting collagen from Alaska Pollock dried skin by hot water were:temperature 80°C,time 9 h,liquid-materials ratio 17 ml/g,and the productivity was45.39%.The collagen of Alaskan Pollock skin was hydrolysated by collagenase.The molecular weight of hydrolysates was less than 1K Da by liquid chromatography.And then these hydrolysates were collagen tri-peptides or their oligomer.The complexation properties of collagen tri-peptide,Glycine-Proline-Hydroxyproline(Gly-Pro-Hyp),anditsdigestionproducts,Glycine(Gly)and Proline-Hydroxyproline(Pro-Hyp),were studied against ferric ion at 25°C,37°C,40°C and 0.15 mol/dm~3 NaCl.The potentiometric data were refined by using Hyperquad 2008 and HySS 2009.The complexes of[MAxHy],with x=1 to 3 and y=-4 to 2,formed in the range of 2 to 11.The complex formation constant(log?)indicated that the complex of Gly-Pro-Hyp was the most stable species and followed by Pro-Hyp and Gly complex.The collagen tri-peptide(Gly-Pro-Hyp),and its digestion products(Gly and Pro-Hyp)were tested in their ability of promoting iron absorption on Caco-2 cell.And all these three ligands mixed with iron(?)had no harm to the Caco-2 cell and improved the content of ferritin at a low concentration.Then Gly,Pro-Hyp and Gly-Pro-Hyp were promising iron absorption promoter.This experiment provided the foundation for the further study of collagen small peptides promoting the iron absorption on the Caco-2 cells.