Identification of two novel antioxidant peptides from edible bird's nest (Aerodramus fuciphagus) protein hydrolysates

Two novel antioxidant pentapeptides were isolated from EBN hydrolysates with a protective effect against H₂O₂-induced oxidative damage in cancer cell lines.

Effect of different pretreatments on functional properties of African catfish (Clarias gariepinus) skin gelatin

Pretreatments with different types of alkali and acid were compared to determine their effects on gelatin extraction from African catfish (Clarias gariepinus) skin. The study was divided into three parts. In the first part, the skins were only treated with alkaline (Ca(OH)2 or NaOH) solution or pretreated with acetic acid solution. For second part, combination of alkali and acid pretreatment was carried out. For the third part, the skins were first treated with NaOH solution, followed by the treatment with acetic acid, citric acid or sulfuric acid solution. Functional properties including the yield of protein recovery, gel strength, viscosity, pH and viscoelastic properties were determined on gelatins obtained with different pretreatment conditions. Pretreatment with alkali removed noncollagenous proteins effectively, whilst acid pretreatment induced some loss of collagenous proteins. Combination of alkali and acid pretreatment not only removed the noncollagenous proteins and caused a significant amount of swelling, but also provided the proper pH condition for extraction, during which some cross-linkages could be further destroyed but with less breakage of intramolecular peptide chains. Pretreatment of catfish skins with 0.2 N NaOH followed by 0.05 M acetic acid improved yield of protein recovery, gel strength, viscosity, melting temperature and gelling temperature of gelatin extract.

ACE inhibitory activity of pangasius catfish (Pangasius sutchi) skin and bone gelatin hydrolysate

Skin and bone gelatins of pangasius catfish (Pangasius sutchi) were hydrolyzed with alcalase to isolate Angiotensin Converting Enzyme (ACE) inhibitory peptides. Samples with the highest degree of hydrolysis (DH) were separated into different fractions with molecular weight cut-off (MWCO) sizes of 10, 3 and 1 kDa, respectively and assayed for ACE inhibitory activity. Skin and bone gelatins had highest DH of 64.87 and 68.48 % after 2 and 1 h incubation, respectively. Results from this study indicated that by decreasing the molecular weight of fractions, ACE inhibitory activity was increased. Therefore, F3 permeates (MWCO < 1 kDa) of skin (IC50 = 3.2 μg/ml) and bone (IC50 = 1.3 μg/ml) gelatins possessed higher ACE inhibitory activity compared to their untreated gelatins and corresponding hydrolyzed fractions. In this study, the major amino acids were Glycine followed by Proline with an increased amount of hydrophobic amino acid content in F3 permeates of skin (4.01 %) and bone (5.79 %) gelatin. Digestion stability against gastrointestinal proteases did not show any remarkable change on ACE inhibition potency of these permeates. It was concluded that alcalase hydrolysis of P. sutchi by-products could be utilized as a part of functional food or ingredients of a formulated drug in order to control high blood pressure.