The effect of different pre-salting methods (brine injection with salt with/without polyphosphates, brining and pickling) on the water and salt distribution in dry salted Atlantic cod (Gadus morhua) fillets was studied with proton and sodium NMR and MRI methods, supported by physicochemical analysis of salt and water content as well as water holding capacity. The study indicated that double head brine injection with salt and phosphates lead to the least heterogeneous water distribution, while pickle salting had the least heterogeneous salt distribution. Fillets from all treatments contained spots with unsaturated brine, increasing the risk of microbial denaturation of the fillets during storage. Since a homogeneous water and salt distribution was not achieved with the studied pre-salting methods, further optimizations of the salting process, including the pre-salting and dry salting steps, must be made in the future.
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Regulations on the exploitation of populations of commercially important fish species and the ensuing consumer interest in sustainable products have increased the need to accurately identify the population of origin of fish and fish products. Although genomics-based tools have proven highly useful, there are relatively few examples in marine fish displaying accurate origin assignment. We synthesize data for 156 single-nucleotide polymorphisms typed in 1039 herring, Clupea harengus L., spanning the Northeast Atlantic to develop a tool that allows assignment of individual herring to their regional origin. We show the method’s suitability to address specific biological questions, as well as management applications. We analyse temporally replicated collections from two areas, the Skagerrak (n = 81, 84, 66) and the western Baltic (n = 52, 52). Both areas harbour heavily fished mixed-origin stocks, complicating management issues. We report novel genetic evidence that herring from the Baltic Sea contribute to catches in the North Sea, and find support that western Baltic feeding aggregations mainly constitute herring from the western Baltic with contributions from the Eastern Baltic. Our study describes a general approach and outlines a database allowing individual assignment and traceability of herring across a large part of its East Atlantic distribution.
Cyclodextrin glucanotransferases (CGTases; EC 2.4.1.19) have mainly been characterized for their ability to produce cyclodextrins (CDs) from starch in an intramolecular transglycosylation reaction (cyclization). However, this class of enzymes can also catalyze intermolecular transglycosylation via disproportionation or coupling reactions onto a wide array of acceptors and could therefore be valuable as a tool for glycosylation.In this paper, we report the gene isolation, via the CODEHOP strategy, expression and characterization of a novel CGTase (CspCGT13) from a Carboxydocella sp. This enzyme is the first glycoside hydrolase isolated from the genus, indicating starch degradation via cyclodextrin production in the Carboxydocella strain. The fundamental reactivities of this novel CGTase are characterized and compared with two commercial CGTases, assayed under identical condition, in order to facilitate interpretation of the results. The comparison showed that the enzyme, CspCGT13, displayed high coupling activity using γ-CD as donor, despite preferentially forming α- and β-CD in the cyclization reaction using wheat starch as substrate. Comparison of subsite conservation within previously characterized CGTases showed significant sequence variation in subsites −3 and −7, which may be important for the coupling activity.
The chemical composition of geothermal fluids may be altered upon ascent from the reservoir to surface by processes including boiling, degassing, mixing, oxidation and water–rock interaction. In an attempt to quantify these processes, a three step model was developed that includes: (1) defining the composition of the end-member fluid types present in the system, (2) quantifying mixing between the end-members using non-reactive elemental concentrations and enthalpy and (3) quantifying the changes of reactive elements including degassing, oxidation and water–rock interaction. The model was applied to geothermal water at Vonarskard, Iceland, for demonstration having temperatures of 3–98 °C, pH of 2.15–9.95 and TDS of 323–2250 ppm, and was thought to be produced from boiled reservoir water, condensed steam and non-thermal water. Most geothermal water represented mixture of non-thermal water and condensed steam whereas the boiled reservoir water was insignificantly mixed. CO2 and H2S degassing was found to be quantitative in steam-heated water, with oxidation of H2S to SO4 also occurred. In contrast, major rock forming elements are enriched in steam-heated water relative to their mixing ratios, suggesting water–rock interaction in the surface zone. Boiled reservoir water observed in alkaline hot springs have, however, undergone less geochemical changes upon ascent to surface and within the surface zone.
This study utilized Life Cycle Assessment (LCA) to quantify the environmental impacts of 1 kg of live-weight Arctic char, cultivated in an Icelandic land-based aquaculture farm. The functional unit included assessments of three different feed types; standard feed with high inclusion levels of marine ingredients (Conv.), experimental feed with high inclusion levels of agricultural ingredients (ECO) and a hypothetical Black soldier fly larvae based feed (BSF). Results of the study indicated that the feed production causes the greatest environmental impacts from all feed types considered. The Black soldier fly based feed demonstrated the best environmental performance of the three feed types. Furthermore, it can be concluded that by increasing agriculture based ingredients at the cost of marine based ingredients, a better environmental performance can be reached. This study demonstrated the importance of feed production for aquaculture in terms of environmental impacts and showed that byoptimizing feed consumption, reducing the amount of fishmeal and fish oil and even creating new types of feed from novel ingredients, the overall impacts of aquaculture can be greatly reduced.
The thermophile Rhodothermus marinus produces extracellular polysaccharides (EPSs) that forms a distinct cellular capsule. Here, the first data on EPS production in strains DSM4252T and MAT493 are reported and compared. Cultures of both strains, supplemented with either glucose, sucrose, lactose or maltose showed that the EPS were produced both in the exponential and stationary growth phase and that production in the exponential phase was boosted by maltose supplementation, while stationary phase production was boosted by lactose. The latter was higher, resulting in 8.8 (DSM4252T) and 13.7 mg EPS/g cell dry weight (MAT493) in cultures in marine broth supplemented with 10 g/L lactose. The EPSs were heteropolymeric with an average molecular weight of 8 × 104 Da and different monosaccharides, including arabinose and xylose. FT-IR spectroscopy revealed presence of hydroxyl, carboxyl, N-acetyl, amine, and sulfate ester groups, showing that R. marinus produces unusual sulfated EPS with high arabinose and xylose content.
Lipid deterioration of mackerel caught in Icelandic waters was studied, as affected by different frozen storage temperatures (−18 °C vs. −25 °C) and seasonal variation (August vs. September). The lipid stability was investigated by analyses of hydroperoxide value (PV), thiobarbituric acid reactive substances (TBARS), free fatty acids, as well as changes in fatty acid composition. Results showed significant lipid deterioration with extended storage time, where the lower storage temperature showed significantly more protective effects. Furthermore, a higher lipid oxidation level was recorded for fish caught in September than in August, although lipid hydrolysis occurred to be greater for fish in August than in September. Moreover, results indicated a rather stable level of omega-3 fatty acid during the whole frozen storage period. The analysis indicated that both lipid oxidation and hydrolysis were affected by the frozen storage temperature and the stability differed with regard to season of catch.
Atlantic mackerel (Scomber scombrus) appears in Icelandic waters during its heavy feeding period, resulting in variation in product quality. Fish caught at different times during the summers of 2012 and 2013 (July, August, September) and at different sites of the Icelandic fishing area (East, Northeast, South and Southeast) were analysed. Measurements of lipid and water content, fatty acid composition, lipid hydroperoxide (PV), thiobarbituric reactive substances (TBARS) and free fatty acids (FFA) were studied with the aim of investigating whether this raw material was suitable for the production of high quality products for human consumption. In general, samples collected during the summer of 2012 showed a better condition than fish from 2013. The results indicated seasonal variation in lipid content and rancidity development. The lowest rancidity values were observed in the middle of the Icelandic catching season, indicating that this raw material was best suited for production of high quality products. Moreover, geographical variation of the mackerel catches had an impact on the saturation of the fatty acids, and appeared as follows: East > Northeast.
Atlantic Mackerel (Scombrus scombrus) is a novel species in Iceland, caught during the heavy feeding period. The feeding has an impact on quality and stability of the products, which requires optimization of storage and processing conditions. Physicochemical changes of brined and un-brined mackerel were analysed during frozen storage (6, 9, 12 months) at −18 °C vs. −25 °C with the aim of investigating the suitability of using well-fed frozen mackerel as raw material for canned and hot-smoked products. Heat treatments to a core temperature of 90 °C (representing canning) and 75 °C (representing hot-smoking) were applied. Prolonged frozen storage showed negative effects on the raw material prior to heat processing due to an increased level of lipid oxidation, where fish stored at −18 °C was of significantly poorer quality than fish stored at −25 °C. Moreover, the results indicated that heat treatment resulting in a core temperature of 75 °C showed higher water content, liquid holding capacity, heating yield as well as lower maximum shear force of texture compared to mackerel heated to a core temperature of 90 °C. Overall, analyses indicated that the fatty summer mackerel was well suitable for production of canned and hot-smoked products.
The oceans represent an understudied resource for the isolation of bacteria with the potential to produce novel secondary metabolites. In particular, actinomyces are well known to produce chemically diverse metabolites with a wide range of biological activities. This study characterised spore-forming bacteria from both Scottish and Antarctic sediments to assess the influence of isolation location on secondary metabolite production. Due to the selective isolation method used, all 85 isolates belonged to the phyla Firmicutes and Actinobacteria, with the majority of isolates belonging to the genera Bacillus and Streptomyces. Based on morphology, thirty-eight isolates were chosen for chemical investigation. Molecular networking based on chemical profiles (HR-MS/MS) of fermentation extracts was used to compare complex metabolite extracts. The results revealed 40% and 42% of parent ions were produced by Antarctic and Scottish isolated bacteria, respectively, and only 8% of networked metabolites were shared between these locations, implying a high degree of biogeographic influence upon secondary metabolite production. The resulting molecular network contained over 3500 parent ions with a mass range of m/z 149–2558 illustrating the wealth of metabolites produced. Furthermore, seven fermentation extracts showed bioactivity against epithelial colon adenocarcinoma cells, demonstrating the potential for the discovery of novel bioactive compounds from these understudied locations.