Casein peptides with inhibitory activity on lipid oxidation in beef homogenates and mechanically deboned poultry meat Karina Rossini, Caciano P.Z. Noren ˜a, Florencia Cladera-Olivera, Adriano Brandelli * Laborato ´rio de Bioquı ´mica e Microbiologia Aplicada, Departamento de Cieˆncia de Alimentos, ICTA, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9500, 91501-970 Porto Alegre, Brazil article info Article history: Received 13 March 2008 Received in revised form 6 November 2008 Accepted 7 November 2008 Keywords: Casein peptides Enzymatic hydrolysis Antioxidant Ground beef Mechanically deboned poultry meat (MDM) abstract Bioactive peptides obtained by enzymatic hydrolysis of casein may have antioxidant activity. In this work, casein peptides were obtained using the proteolytic enzymes Alcalase and Flavourzyme. Casein was hydrolyzed for 4 h at 50  C and pH 8, and the resulting peptides were analyzed. The enzymatic hydrolysis with Flavourzyme resulted in higher concentration of soluble protein and free amino acids, and produced peptides with lower molecular mass than those obtained with Alcalase, as observed by gel permeation chromatography and polyacrylamide gel electrophoresis. Casein peptides obtained with Flavourzyme also exhibited greater antioxidant capacity using the ABTS radical method. Casein peptides (20 mg ml 1 ) effectively inhibited lipid peroxidation in ground beef homogenates and mechanically deboned poultry meat. Casein peptides may be useful in meat processing as another naturally occurring antioxidant, helping to prevent off-flavor formation in meat products and increasing shelf life. Ó 2008 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved. 1. Introduction Milk and milk components have been frequently used in the enhancement of nutritional and technological properties of a wide variety of foods, as well as in adding the desired flavor to them (Tunçtu ¨ rk & Zorba, 2006). The biological and physiological activities of milk proteins are partially attributed to several peptides encoded in the native protein molecules (Kim, Jang, & Kim, 2007). They can be produced in vitro by enzymatic hydrolysis. The enzymatic hydrolysis of proteins has been extensively used to produce food ingredients with improved functional and nutritional properties (Lemieuxa, Amiota, Piotb, & Guillochon, 1997). Protein hydrolysates can be classified into three major groups depending on the degree of hydrolysis, which determines their applications: (a) hydrolysates with a low degree of hydrolysis with improved functional proper- ties, (b) hydrolysates with a variable degree of hydrolysis that are mostly used as flavorings, and (c) extensive hydrolysates that are mostly used as nutritional supplements and in special medical diets (Pedroche et al., 2004). Hydrolysis of milk protein has for long been employed, using e.g. trypsin (Pintado, Pintado, & Malcata, 1999). In particular, casein hydrolysates obtained by the proteases trypsin and chymotrypsin contain more than 200 peptides of different sizes (Sakanaka, Tachibana, Ishihara, & Juneja, 2005) and have smaller molecular masses and less secondary structure than intact proteins (Fitzgerald, 1998). The commercial enzyme Alcalase has been used to hydrolyze milk caseins, resulting in products showing potential anti-hypertensive activity and antioxidant capacity (Kim et al., 2007; Mao, Ni, Sun, Hao, & Fan, 2007). Another commercial enzyme, Flavourzyme, was used to accelerate cheddar cheese ripening (Kailasapathy & Lam, 2005). The hydrolysates are better absorbed than a mixture of free amino acids, which may be due to the size and nature of the peptides during the digestive process (Sakanaka et al., 2005). Among the biologically active peptide molecules, the phosphory- lated caseinophosphopeptides (CPP), are known to exert an effect on calcium bioavailability but also on other minerals because of the highly anionic character of CPP, which make them resistant to further hydrolysis by proteases and allow them to form soluble complexes with calcium (Fitzgerald, 1998; Kitts, 2005). The ability of CPP to scavenge free peroxyl radicals as well as to chelate transition metals such as iron, copper, and zinc has been reported (Kim et al., 2007). The chelation of transition metals by CPP might originate from phosphoseryl and glutamyl residues contained in a-, b-, and k-casein (Meisel, 1997), which differ from each other in their phosphate content (Sakanaka et al., 2005). The scavenging capacity of CPP against free peroxyl radicals has been demonstrated to be positively correlated with the amounts of histidine, lysine, proline, and tyrosine that might contribute to the antioxidant activities of some proteins and peptides (Kim et al., 2007). It has been suggested that CPP could be used as antioxidants to prevent oxida- tive damage to muscle foods (Sakanaka et al., 2005). * Corresponding author. Tel.: þ55 51 3316 6249; fax: þ55 51 3308 7048. E-mail address: abrand@ufrgs.br (A. Brandelli). Contents lists available at ScienceDirect LWT - Food Science and Technology journal homepage: www.elsevier.com/locate/lwt 0023-6438/$34.00 Ó 2008 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.lwt.2008.11.002 LWT - Food Science and Technology 42 (2009) 862–867