Fractionation of Protein Hydrolysates of Fish and Chicken Using Membrane Ultrafiltration: Investigation of Antioxidant Activity Graciela Salete Centenaro & Myriam Salas-Mellado & Carla Pires & Irineu Batista & Maria L. Nunes & Carlos Prentice Received: 21 February 2013 /Accepted: 6 January 2014 / Published online: 22 January 2014 # Springer Science+Business Media New York 2014 Abstract In this work, chicken and fish peptides were obtained using the proteolytic enzymes α-Chymotrypsin and Flavourzyme. The muscle was hydrolyzed for 4 h, and the resulting peptides were evaluated. Hydrolysates were produced from Argentine croaker (Umbrina canosai) with a degree of hydrolysis (DH) of 25.9 and 27.6 % and from chicken (Gallus domesticus) with DH of 17.8 and 20.6 % for Flavourzyme and α-Chymotrypsin, respectively. Membrane ultrafiltration was used to separate fish and chicken hydrolysates from Flavourzyme and α-Chymotrypsin based on molecular weight cutoff of >1,000, <1,000 and >500, and <500 Da, to produce fractions (F1,000, F1,000–500, and F500) with antioxidant activity. Fish hydrolysates produced with Flavourzyme (FHF) and α-Chymotrypsin showed 60.8 and 50.9 % of peptides with a molecular weight of <3 kDa in its composition, respectively. To chicken hydrolysates produced with Flavourzyme and α-Chymotrypsin (CHC) was observed 83 and 92.4 % of peptides with a molecular weight of <3 kDa. The fraction that showed, in general, higher antioxidant potential was F1,000 from FHF. When added 40 mg/mL of FHF and CHC, 93 and 80 % of lipid oxidation in ground beef homogenates was inhibited, respectively. The composition of amino acids indicated higher amino acids hydrophobic content and amino acids containing sulfuric residues for FHF, which showed antioxidant potential. Keywords Antioxidant activity . Chicken . Fish . Hydrolysate . Peptides . Ultrafiltration membranes Appl Biochem Biotechnol (2014) 172:2877–2893 DOI 10.1007/s12010-014-0732-6 G. S. Centenaro : M. Salas-Mellado : C. Prentice (*) Laboratory of Food Technology, School of Chemistry and Food, Federal University of Rio Grande (FURG), 96201-900 Rio Grande, Rio Grande do Sul, Brazil e-mail: dqmprent@furg.br C. Pires : I. Batista : M. L. Nunes Portuguese Institute of Sea and Atmosphere (IPMA, I. P./DMRM), Av. Brasília, 1449-006 Lisbon, Portugal