Development of antioxidant peptide fractions from egg yolk proteins using enzymatic hydrolysis and ultrafiltration membranes
|Authors:||Chay Pak Ting, Bertrand|
|Advisor:||Gauthier, Sylvie; Pouliot, Yves|
|Abstract:||Delipidated egg yolk proteins are considered as a by-product in the process of the lipid and protein separation. The major proportion of yolk protein exits as lipoproteins except for phosvitin and livetins. Hen egg yolk phosphopeptides from phosvitin have demonstrated free radical scavenging and antioxidant activities against lipid peroxidation. Moreover, phosphopeptides have also been shown to provide an effective defense against oxidative stress in human intestinal epithelial cells. However, the method for producing these peptides was not applicable at large scale. The goal of this study was to develop and scale up the production of phosvitin from a commercially available delipidated egg yolk proteins and the production of antioxidant egg peptides by mean of enzymatic hydrolysis and ultrafiltration (UF). Egg yolk phosvitin was concentrated and desalted from delipidated egg yolk protein by a process that involved first a salting-out with 10% NaCl (w/w) treatment followed by UF and diafiltration. Various filtration parameters such as pH, feed concentration, transmembrane pressure and molecular weight cut-off (MWCO) membranes were studied. Results showed that performance of the 10 and 30 kDa MWCO UF membranes tested were similar in terms of production and desalting capacity. However, difference in terms of permeation flux during UF was noticed with the use of the 30 kDa MWCO membrane. Two-dimensional gel electrophoresis was performed to characterize the protein composition of the commercially delipidated egg yolk proteins and its UF-fractions obtained previously. Most of the vitellogenin cleavage products were identified in the crude phosvitin. Nevertheless, as compared to protein composition of fresh egg yolk, the UF-retentate profiles showed different patterns which suggest that egg yolk protein composition is modified as a result of UF-concentration. Fractionation of phosphopeptides by sequential UF with MWCO of 5 kDa and 1 kDa was performed to produce peptide fractions with increased antioxidant capacity. Antioxidant capacity was quantified by oxygen radical absorbance capacity (ORAC) assay to determine proton-donating capacities of the egg yolk hydrolysates. The peptide fractions with the greatest antioxidant capacity (1501.1–1886.8 µM TE.g-1 protein) were produced by enzymatic hydrolysis with trypsin alone and presented some common features such as low molecular weight, composition in amino acids and phosphorus content. The enzymatic hydrolysis of phosphoproteins from commercially delipidated egg yolk proteins obtained by UF successfully produced peptide fractions with antioxidant activity, which can be increased through fractionation. The process studied in this project offers the possibility to produce egg yolk peptides with potential uses in functional and nutraceutical applications.|
|Document Type:||Thèse de doctorat|
|Open Access Date:||18 April 2018|
|Collection:||Thèses et mémoires|
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