Characterization of protein hydrolysates and lipids obtained from black scabbardfish (Aphanopus carbo) by-products and antioxidative activity of the hydrolysates produced I. Batista *, C. Ramos, J. Coutinho, N.M. Bandarra, M.L. Nunes INRB/IPIMAR, Av. Brası´lia, 1449-006 Lisbon, Portugal 1. Introduction The fishery of black scabbard fish (Apanopus carbo) in the Portuguese continental waters started in the 1980s. In last years the landings of this species in the continental fishing harbours has been around 3000 metric tons. Black scabbardfish is a deep sea fish caught by long lines at depths around 1000 m. It is mostly sold eviscerated with head on but it is also processed into fillets and sold as fresh fillets. The by-products generated in the filleting process are mainly constituted by heads, some viscera, skin, backbone and trimmings. This material is usually reduced into fish meal. However, these proteinaceous by-products may be also upgraded by converting them in fish protein hydrolysates (FPH), which has been recognized as an alternative to upgrading these raw materials in many works [1– 5]. The production of FPH also enables the recovery of bones and skins present in the by-products, which can be used for the extraction of high added value products. FPH present a wide range of potential applications, which include the use in animal feeds [6–10], foods [11–13] or microbial growth media [14–20]. FPH also exhibits antioxidant properties such as reported by several authors [4,21–28] and constitute a source of health beneficial molecules such as secretagogues, calciotropic hormones and growth factors [29–32]. In addition hypotensive activity [33–35], immuno-stimulant activity [36,37], and antiproliferative activity [38] has been found as well. The production of protein hydrolysates has been also used as a tool for the lipid recovery from by-products [39,40,41]. The mild temperature conditions used in this method makes it suitable to hamper autoxidative changes occurring in the highly unsaturated fatty acids present in marine lipids. The beneficial health effects of these lipids are well documented and have increasing applications in foods and feeds for aquaculture, healthcare and pharmaceutical products. The aim of this study was to produce a protein hydrolysate from BSB with different DH using Protamex, to characterize the lipid fraction and to evaluate the antioxidative activities of the hydrolysates obtained. 2. Materials and methods 2.1. Raw material Fresh black scabbardfish (Aphanopus carbo) by-products (heads, viscera, frames, skin, trimmings) from the filleting industry were ground and immediately frozen in 100 g plastic bags and stored at 20 8C until use. 2.2. Enzymes The food-grade enzyme Protamex TM (EC. 3.4.21.14/3.4.24.28) a protease complex from Bacillus subtilis with optimal working conditions at 35–60 8C and at pH 5.5–7.5 was provided by Novo Nordisk (Bagsvaerd, Denmark). Process Biochemistry 45 (2010) 18–24 ARTICLE INFO Article history: Received 29 April 2009 Received in revised form 11 July 2009 Accepted 23 July 2009 Keywords: Black scabbardfish By-products Fish protein hydrolysates Lipids Fatty acids Antioxidative activity ABSTRACT The preparation of protein hydrolysates from black scabbardfish (Aphanopus carbo) by-products (BSB) was studied as an alternative for the upgrading of this raw material. Different levels of Protamex TM were used in the hydrolysate preparation and the peptides obtained and the lipids present in each of the four fractions obtained after centrifugation of the hydrolysed material were characterized. The nitrogen solubilization achieved was around 83% and degree of hydrolysis (DH) was about 57%. A high proportion of the peptides had molecular weights lower than 1000 Da. The highest percentage of oil remained in the emulsion (50–65%) and the highest percentage of free oil obtained was ca. 36%. The fatty acid profile of lipids present in the BSB and in the different fractions was similar. The triacylglycerols were dominant in all fractions and the highest percentage of phospholipids was detected in the oil from sludge and hydrolysate, followed by the emulsion but they were not present in the free oil. Cholesterol and cholesterol esters were detected in all fractions at low levels. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activity and the reducing power of BSB hydrolysates increased with increasing DH. However, the hydroxyl scavenging activity decreased with DH. ß 2009 Elsevier Ltd. All rights reserved. * Corresponding author. Fax: +351 21 301 59 48. E-mail address: irineu@ipimar.pt (I. Batista). Contents lists available at ScienceDirect Process Biochemistry journal homepage: www.elsevier.com/locate/procbio 1359-5113/$ – see front matter ß 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.procbio.2009.07.019