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Whole body saline-perfused rainbow trout (Oncorhynchus mykiss) was ice-stored for 4 weeks and compared with unwashed/washed minces from unbled and bled trout in terms of rancid odour, peroxide value (PV), thiobarbituric acid reactive substances (TBARS) and redness loss. Muscle from saline-perfused fish, which had 72% less total haem, was deficient in rancid odour during the whole storage, while bled (54% less haem) and unbled samples developed rancid odour already after ~4 and 2 days; higher intensity without bleeding. PV/TBARS also developed in the order unbled > bled > perfused samples; however, PV/TBARS were not as completely prevented as rancid odour after perfusion. Saline washing (3 × 3 volumes) of unbled mince removed 84% haem and yielded the second most stable sample while saline washing (1 × 1 volumes) destabilised unbled mince, despite 64% haem removal. Concurrent antioxidant removal during washing of minces obviously counteracted the effect of blood removal and washing fish mince with small volumes of solution should be used with great care.

The effect of microbial transglutaminase (M‐TGase) (0–0.6 units g−1 sample) and setting condition (25 °C/180 min, 30 °C/120 min, 35 °C/60 min and 40 °C/30 min) on gel properties of blend protein isolate of gutted kilka and silver carp was studied. The protein isolate provided a good substrate for M‐TGase activity so that a low amount of M‐TGase (0.2 unit g−1 sample) substantially improved textural properties and water holding capacity (WHC) of the gels. Breaking force of the gels was positively affected by M‐TGase up to 0.6 unit g−1 sample, but it negatively affected their WHC. Prior setting at 25–35 °C increased the breaking force of proteins compared to directly heated gel, resulting in maximum breaking force at 35 °C/60 min. However, the setting at 40 °C/30 min caused proteolysis, which was reflected in higher amounts of TCA‐soluble peptides and gel weakening. Denser microstructure and higher myosin heavy chain polymerisation observed in the gels which experienced the setting was well correlated with improvement in textural properties.

In this study, fish muscle press juice, PJ, was evaluated as an antioxidative liquid for glazing of fish fillets prior to frozen storage. PJ has in previous studies efficiently protected fish mince lipids against haemoglobin- mediated oxidation. Frozen herring fillet were glazed with water, PJ or 50 mM phosphate buffer of the same pH as herring PJ (6.5). Over 52 weeks, peroxide value (PV), TBA-reactive substances (TBARS), rancid odour and colour were monitored. From 26 to 52 weeks, water-glazed fillets were significantly (P < 0.05) more oxidised compared to fillets glazed with PJ or buffer, most clearly shown by PV and TBARS data. The protective effects of both PJ and buffer compared to water could indicate a role, for example, of the physiological ionic strength. The finding that PV became elevated in PJ which was frozen stored alone in a thin layer indicates that PJ stripped from, for example, trace lipids and haemoglobin would provide better protection.

BACKGROUND The ability of different in vitro antioxidant assays to predict the efficiency of cod protein hydrolysate (CPH) and Fucus vesiculosus ethyl acetate extract (EA) towards lipid oxidation in hemoglobin fortified washed cod mince and iron containing cod liver oil emulsion was evaluated. Progression of oxidation was followed by sensory analysis, lipid hydroperoxides and TBA-reactive substances (TBARS) in both systems, as well as redness loss and protein carbonyls in the cod system. RESULTS The in vitro tests revealed high reducing capacity, high DPPH radical scavenging properties and high ORAC-value of the EA which also inhibited lipid and protein oxidation in the cod model system. The CPH had high metal chelating capacity and was efficient against oxidation in the cod liver oil emulsion. CONCLUSION The results indicate that the F. vesiculosus extract has a potential as an excellent natural antioxidant against lipid oxidation in fish muscle foods while protein hydrolysates are more promising for fish oil emulsions. The usefulness of in vitro assays to predict the antioxidative properties of new natural ingredients in foods thus depends on the knowledge about the food systems, particularly the main pro-oxidants present.

BACKGROUND Upon oxidation of the polyunsaturated fatty acids in fish oil, either before ingestion or, as recently shown, during the gastro-intestinal passage, a cascade of potentially cytotoxic peroxidation products, such as malondialdehyde and 4-hydroxy-2-hexenal, can form. In this study, we digested fresh and oxidised cod liver oils in vitro, monitored the levels of lipid peroxidation products and evaluated oxidative, proteomic and inflammatory responses to the two types of digests in the yeast Saccharomyces cerevisiae and human monocyte-derived dendritic cells. RESULTS Digests of cod liver oil with 22–53 µmol L−1 malondialdehyde and 0.26–3.7 µmol L−1 4-hydroxy-2-hexenal increased intracellular oxidation and cell energy metabolic activity compared to a digested blank in yeast cells and the influence of digests on mitochondrial protein expression was more pronounced for oxidised cod liver oil than fresh cod liver oil. The four differentially expressed and identified proteins were related to energy metabolism and oxidative stress response. Maturation of dendritic cells was affected in the presence of digested fresh cod liver oil compared to the digested blank, measured as lower CD86 expression. The ratio of secreted cytokines, IL-12p40/IL-10, suggested a pro-inflammatory effect of the digested oils in relation to the blank (1.47–1.67 vs. 1.07). CONCLUSION Gastro-intestinal digestion of cod liver oil increases the amount of oxidation products and resulting digests affect oxidation in yeast and immunomodulation of dendritic cells. © 2014 Society of Chemical Industry

Background: Little is known about the relation between haemoglobin (Hb)-mediated lipid and protein oxidation in muscle foods and how these two reactions can be inhibited by naturally occurring antioxidants. This study was aimed at evaluating (1) lipid oxidation and protein oxidation induced by 20 μmol L Hb during chilled and frozen storage of washed codmince and (2) the efficiency of 10-1000 ppm (0.063-6.3 mmol L -1 ) caffeic acid in preventing these reactions. Results: Addition of 20 μmol L -1 Hb increased peroxide value (PV), rancid odour, protein carbonylation, protein insolubilisation, redness loss and α-tocopherol loss in ice-stored washed cod mince. Since both lipid and protein oxidation developed at the same time, it was not possible to conclude which reaction initiated the other. All studied reactions were efficiently inhibited by ≥50 ppm caffeic acid, which could be a result of α-tocopherol regeneration, general radical scavenging, reduced formation of oxidised Hb forms and/or conformational changes in Hb structure. During frozen storage the only clear effect of Hb was increased PV, and here caffeic acid was less efficient as an antioxidant. Conclusion: Hb-induced lipid and protein oxidation occurred quickly in ice-stored washed cod mince, and the two reactions could not be separated in time. During frozen storage, Hb caused only limited lipid oxidation. Caffeic acid (≥50 ppm) was an efficient antioxidant during ice storage. © 2010 Society of Chemical Industry.

AIM: Few dietary studies have looked beyond fish oil to explain the beneficial metabolic effects of a fish-containing diet. Our aim was to study whether addition of herring, or sub-fractions of herring, could counteract negative metabolic effects known to be induced by a high-fat, high-sugar diet. METHODS: Rats were given six different diets: standard pellets; high energy diet with chicken mince (HiE control); high energy diet with herring mince (HiE herring); and high energy diet with chicken mince and either herring oil (HiE herring oil), herring press juice, PJ (HiE PJ) or herring low molecular weight PJ (HiE LMW-PJ). Factors associated with the metabolic syndrome were measured. RESULTS: There were no differences in energy intake or body weight between the groups, but animals fed high energy diets had a higher body fat content compared with the pellet group, although not statistically significant in all groups. Mesenteric adipocyte size was smaller in the HiE herring oil group compared with the HiE control. Glucose clamp studies showed that, compared with the pellet group, the HiE control and HiE herring diets, but not the HiE herring oil diet, induced insulin resistance. Addition of herring or herring oil to the high energy diet decreased total cholesterol levels, triacylglycerols and the atherogenic index compared with the HiE control group. CONCLUSIONS: The results suggest that addition of herring or herring oil counteracts negative effects on blood lipids induced by a high energy diet. The lipid component of herring thus seems to be responsible for these beneficial effects.

This study was conducted to evaluate the effect of skinning and of compositional differences on the oxidative stability of various horizontal layers from herring (Clupea harengus) during frozen storage. Herring fillets, with and without skin, were stored at -18°C for 0, 3, 9, 16 and 28 weeks. After each storage period, the fillets were divided horizontally into three layers: ‘under skin’, ‘middle part’ and ‘inner part’. Each layer was then extracted for total lipids, in which peroxide value (PV), absorbance at 234 nm (A234) and 268 nm (A268) as well as lipid-soluble fluorescent oxidation products (FP) were measured. Prior to storage, the fat content, fatty acid pattern and α-tocopherol were also analysed. During storage of skinless fillets, the under skin layer increased most in PV, A234, A268 and FP (P

The demand for healthymarine omega‐3 polyunsaturated fatty acids (PUFA) for feed, functional foods, and pharmaceutical products is increasing. Formany years fish oil produced fromwild fish has been the most important source of marine omega‐3 PUFA. However, the production of fish oil has been stable during the last decade and is not expected to increase due to sustainability reasons. Therefore, to meet the shortage in marine omega‐3 PUFA expected in the near future, new sources of these fatty acids for feed, food and pharmaceutical products are required. In November 2012, a joint meeting between theMarine Lipid Division from EuroFedLipid and the Nordic LipidForum was held in Copenhagen in order to share knowledge about recent progress in this area and to discuss future solutions to meet the demands for omega‐3 PUFA. The one and a half days programme included 24 oral presentations and 10 posters. The first two presentations at the meeting gave an overview of the worldwide situation for omega‐3 supply and the future demand. It has been estimated that by 2025 the demand for crude fish oil for dietary supplements and functional foods will reach 450 000 tons/year, which accounts for almost 50% of today’s global fish oil supply. At the same time, the demand for marine omega‐3 PUFA for aquaculture will also increase significantly. The current production ofmarine omega‐ 3 PUFA cannot meet these demands. Two presentations provided an overview on the current status in developing transgenic plants that are able to produce long chain omega‐3 PUFA. From these presentations, it was clear that this strategy is possible, but further development is still necessary to increase yields. Nevertheless, it is expected that such oils will be available on the market within the next 5–10 years. Other new sources such as microalgae, krill, discarded species (by‐catches from fisheries), rest raw materials and waste water from, e.g. the herring industry were also discussed. Omega‐3 rich oils produced by heterotrophic algae are already commercially available today and are successfully used for example in infant formula. There is an increasing interest in phototrophic microalgae as these can be grown with CO2 as the only carbon source. At the meeting it was demonstrated that such microalgae can be used in animal feed. Krill oil is a good source of omega‐3 PUFA, which to a high extent are found in the phospholipid form, which seems to be more bioavailable than omega‐3 PUFA in the triacylglycerol form. Oxidation mechanisms in krill oil are, however, more complex than in fish oil as the lipids can degrade to form Strecker aldehydes and pyrroles. Therefore, the traditional methods for measuring oxidation (PV and AV) are not suitable for quality control of krill oils. Discarded species and wastewater from the herring industry were shown to be able to provide substantial amounts of omega‐3 PUFA.Using discarded species and rest rawmaterials from the fish industry, oils can be extracted in the same way as from traditional fish used for fish oil production. Regarding wastewater, developments within up‐concentration/filtration techniques are required before this source can be utilized commercially. Such development is underway. Several presentations concerned the possibility of feeding fish with alternative feed sources to fish meal and fish oil, and the effect on fish composition and metabolism was discussed. Six papers from the meeting are published in this special collection. The collection is published in two parts, three papers were featured already in the September issue and this issue brings the second part. The Collection is accessible online at http://onlinelibrary.wiley.com/ journal/10.1002/(ISSN)1438‐9312/homepage/novel_sources_of_omega‐3.htm. Hopefully, these articles will be a source of inspiration to more research and development in this important topic as this is urgently needed.