Salted herring brine as a coating or additive for herring (Clupea harengus) products — A source of natural antioxidants? Irene Albertos a, ⁎, Nina Gringer b , Daniel Rico a , Caroline P. Baron b a Agrarian Technological Institute of Castilla and Leon (ITACyL), Junta de Castilla y León, Consejería de Agricultura y Ganadería, Finca Zamadueñas, Ctra. Burgos, Km 119, 47071 Valladolid, Spain b Technical University of Denmark, National Food Institute, Division of Industrial Food Research, Søltoft Plads, Building 221, 2800 Kgs Lyngby, Denmark abstract article info Article history: Received 31 October 2015 Received in revised form 30 August 2016 Accepted 5 September 2016 Available online 6 September 2016 The objective of this study was to characterise herring brine and assess its use as natural antioxidant in herring preservation. Herring brines from different marinated products (brine from fillet-ripened spice-cured herring SC, traditional barrel-salted spice-cured herring TSp and brine from traditional barrel-salted herring TSa) were used without any pre-treatment or with a previous pH adjustment, and tested either as coating agents (glazing) for frozen herring or additives in fresh mince herring, in order to prevent oxidation. TSa and TSp were the most effective glazing agents, retarding lipid oxidation. Brines tested as additive retarded lipid and protein oxidation in a similar trend than herring mince containing salt and/or protein. SC brine was more efficient against lipid and protein oxidation when compared to the other tested brines. Using protein fractions isolated from herring marinating brines as glazing or additive seems feasible for preventing oxidation of both frozen and fresh herring. © 2016 Elsevier Ltd. All rights reserved. Keywords: Herring (Clupea harengus) Brine pH-shift Glazing Oxidation Natural antioxidant 1. Introduction Barred-salted herring is an important fish product in the Nordic fish- ery industry whilst in the South of Europe anchovies are more common as salted product. Herring is one of the most important species in the fishing industry in Northern Europe. In 2010/2011 approximately 1.000.000 tons of herring were landed in Nordic Countries, which most ends up as salted product (Baron et al., 2015). The production of salted herring has always been of special interest in the Scandinavian countries for centuries, probably originating in the eight century (Voskresensky, 1965) as a preservation process. During the salting process a long maturation period takes place, where degradation of proteins occurs due to both digestive and muscle proteases (Nielsen, 1995). During this long ripening period transport of biomolecules such as proteins, lipids and peptides leach out from the fish to the brine (Svensson, Nielsen, & Bro, 2004), leading to a brine rich in organic matter. After the ripening period, the maturating brine is removed and discarded and, before barred-salted herring's commercialisation, the fish is packed with fresh brine containing spices and flavourings. During the production, very large volumes of brine with high organic load are discarded. Specifically, 100 L of brines are generated per 100 kg of herring produced during the maturation step (Gringer et al., 2015). Therefore, there is a need to demonstrate if this liquid waste, which contains high-value marine biomolecules such as protein, lipids and peptides, could be re-utilised and valorised. Furthermore, marinating brine is a food grade waste and could repre- sent a good source of natural additives with antioxidant properties. Her- ring brines have previously been characterised, containing proteins and peptides (Gringer, Osman, Nielsen, Undeland, & Baron, 2014) which may be able to protect lipids from oxidative damage during herring rip- ening (Andersen, Andersen, & Baron, 2007). Proteins might play a role in scavenging free radicals that could otherwise damage proteins. The released iron from the muscle to the brine might attack protein rather than inducing lipid oxidation in Fenton type reaction. Proteins have also been found to act as antioxidants, as they form stable and long- life protein hydroperoxides, and prevent propagation of oxidative reac- tions, protecting lipids from oxidative damage (Baron, Berner, Skibsted, & Refsgaard, 2005). A recent study characterising brines from different Scandinavian products demonstrated their radical scavenging and iron chelating ac- tivities, and reducing properties using in vitro tests (Gringer et al., 2014). Similarly, a previous study showed herring press juice preventing oxidative reactions in a fish model system and a simulated gastrointestinal digestion, antioxidant capacity that was attributed to low molecular weight compounds (Sannaveerappa, Sandberg, & Undeland, 2007a; Sannaveerappa, Carlsson, Sandberg, & Undeland, 2007b). Recently, Taheri, Farvin, Jacobsen, and Baron (2014) isolated protein fractions from barrel-salted herring brines and reported that they exhibit good antioxidant properties in vitro and in simple emulsions system of 5% of fish oil in water emulsion. However, despite their potentially interesting antioxidant properties, no studies have demonstrated the valorisation of this protein-rich waste using Innovative Food Science and Emerging Technologies 37 (2016) 286–292 ⁎ Corresponding author. E-mail address: albmunir@itacyl.es (I. Albertos). http://dx.doi.org/10.1016/j.ifset.2016.09.008 1466-8564/© 2016 Elsevier Ltd. All rights reserved. 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