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This study aimed at limiting hemolysis of fish red blood cells (RBCs) as a strategy to limit hemoglobin (Hb)-induced lipid oxidation during post-mortem handling and processing. Effects of varying temperature, salinity, and mechanical impact were studied using washed resuspended RBCs (wr-RBCs) and whole blood (WB) from rainbow trout (Oncorhynchus mykiss) and herring (Clupea harengus). The wr-RBCs were most stable avoiding mechanical stress, keeping isotonic conditions (0.9–1.3% NaCl) and low temperature 0–6 °C, with predicted minimum at 2.5 °C. When compared at the same salinity, it was found that hemolysis was more pronounced in herring than trout wr-RBCs. Furthermore, WB was more stable than wr-RBCs, showing protecting the effects of blood plasma. Studying individual plasma components, stabilizing effects were found from glucose, proteins, and ascorbic acid. This study indicates that small adjustments in the early handling and processing of fish such as changing salinity of storage and rinsing solutions could minimize Hb contamination of the fish muscle and thereby improve quality.

Ulva fenestrata is an economically and ecologically important green algal species with a large potential in seaweed aquaculture due to its high productivity, wide environmental tolerance, as well as interesting functional and nutritional properties. Here, we performed a series of manipulative cultivation experiments in order to investigate the effects of irradiance (50, 100, and 160 μmol photons m−2 s−1), temperature (13 and 18 °C), nitrate (pCO2 (200, 400, and 2500 ppm) on the relative growth rate and biochemical composition (fatty acid, protein, phenolic, ash, and biochar content) in indoor tank cultivation of Swedish U. fenestrata. High irradiance and low temperature were optimal for the growth of this northern hemisphere U. fenestrata strain, but addition of nutrients or changes in pCO2 levels were not necessary to increase growth. Low irradiance resulted in the highest fatty acid, protein, and phenolic content, while low temperature had a negative effect on the fatty acid content but a positive effect on the protein content. Addition of nutrients (especially nitrate) increased the fatty acid, protein, and phenolic content. High nitrate levels decreased the total ash content of the seaweeds. The char content of the seaweeds did not change in response to any of the manipulated factors, and the only significant effect of changes in pCO2 was a negative relationship with phenolic content. We conclude that the optimal cultivation conditions for Swedish U. fenestrata are dependent on the desired biomass traits (biomass yield or biochemical composition).

In recent years, the interest in using seaweed for the sustainable production of commodities has been increasing as seaweeds contain many potentially worthwhile compounds. Thus, the extraction and refining processes of interesting compounds from seaweeds is a hot research topic but has been found to have problems with profitability for novel applications. To increase the economic potential of refining seaweed biomass, the content of the compounds of interest should be maximized, which can potentially be achieved through optimization of cultivation conditions. In this study, we studied how the monosaccharide composition of the green seaweed species Ulva fenestrata is influenced by the abiotic factors; irradiance, temperature, nitrate, phosphate, and pCO2. It was evident that lower nitrate concentration and cultivation at elevated temperature increased monosaccharide contents. A 70% increase in iduronic acid and a 26% increase in rhamnose content were seen under elevated irradiance and temperature conditions, though the absolute differences in monosaccharide concentration were small. Irradiance and nitrate impacted the ratio between iduronic and rhamnose, which is an indicator of the ulvan structure. These results could potentially be utilized to coax the ulvan towards specific bioactivities, and thus have a considerable impact on a potential biorefinery centered around Ulva.

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.

Structural, functional and nutritional properties of protein recovered from brown seaweed, S. latissima with alkaline solubilization/isoelectric precipitation as a function of different post-harvest stabilization methods were studied. The latter included freezing at −20 °C/-80 °C, oven-drying, sun-drying, freeze-drying and ensilaging. Also, the efficacy of freeze/thaw-aided precipitation (F/T) in improving protein recovery of the process was evaluated. The freeze-dried, oven-dried, and −20 °C frozen seaweeds resulted in significantly higher protein yield than the −80°C-frozen, sun-dried and ensiled biomasses. F/T increased protein precipitation and doubled total protein yield. Sun-drying and −20°C-freezing caused extensive protein degradation as revealed by SDS-PAGE and HP-SEC, while oven-drying altered the seaweed protein structure with less α-helices. Functional properties of the seaweed proteins were remarkably affected by stabilization condition and F/T, but nutritional value of the proteins was only dependent on stabilization method. Thus, to efficiently recover seaweed proteins, its post-harvest stabilization condition must be carefully chosen based on the final application of the proteins.

Seaweed is a promising sustainable source of vegan protein as its farming does not require arable land, pesticides/insecticides, nor freshwater supply. However, to be explored as a novel protein source the content and nutritional quality of protein in seaweed need to be improved. We assessed the influence of pH-shift processing on protein degree of hydrolysis (%DH), protein/peptide size distribution, accessibility, and cell bioavailability of Ulva fenestrata proteins after in vitro gastrointestinal digestion. pH-shift processing of Ulva, which concentrated its proteins 3.5-times, significantly improved the %DH from 27.7±2.6% to 35.7±2.1% and the amino acid accessibility from 56.9±4.1% to 72.7±0.6%. Due to the higher amino acid accessibility, the amount of most amino acids transported across the cell monolayers was higher in the protein extracts. Regarding bioavailability, both Ulva and protein extracts were as bioavailable as casein. The protein/peptide molecular size distribution after digestion did not disclose a clear association with bioavailability.

Lipid oxidation in ice-stored sorted herring fractions (head, backbone, viscera+belly flap, tail, fillet) from spring and fall, and its association with endogenous prooxidants, antioxidants and lipid substrates were investigated. Peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) had increased significantly in all fractions after 1 day, but for both seasons, the most rapid PV and TBARS development occurred in head, which also had highest hemoglobin (Hb) levels and lipoxygenases (LOX) activity. Viscera+belly flap was overall the most stable part, and also had the highest α-tocopherol content. Pearson correlation analyses across all five fractions confirmed a significant impact of Hb, LOX and α-tocopherol on the lipid oxidation susceptibility, while content of total iron, copper, lipids or polyunsaturated fatty acids provided no significant correlation. Overall, the study showed which pro-oxidants that should be inhibited or removed to succeed with value adding of herring filleting co-products -and the fillet itself.

One approach to ongrow juvenile European lobster, Homarus gammarus, is to utilize land based rearing systems, incorporating automated feeding, individual culture and provision of stable pelleted feeds, preferably using sustainable ingredients. We initiated three feeding experiments to investigate the general suitability of ingredients produced from seafood by-products as novel feeds for H. gammarus, in terms of promoting survival, development and growth of post-larval lobsters from post-larvae (PL) stage IV to the first juvenile stage (stage V). The first experiment was designed to screen an array of candidate, locally produced, novel protein sources on growth performance parameters. This initial experiment revealed that PL reared on a raw (i.e. wet, unprocessed shrimp) feed used as a reference showed superior performance to those reared on experimental feeds containing fishmeal, herring protein isolate or mussel meal; however, a novel type of shrimp meal, produced by flocculation from waste water, promoted the best PL performance of any experimental feed. A second experiment was designed to test the effect of drying method and to optimize the form of a wet shrimp reference feed used by lobster hatcheries. This showed that the performance of PL reared on experimental freeze-dried shrimp feed was not significantly different to those reared on the wet, unprocessed shrimp used as a reference feed. However, lobsters offered experimental oven-dried shrimp feed (with or without an immune supplement) resulted in significantly lower survival or growth performance. A third and final experiment was designed in an attempt to improve a candidate herring-based protein source, by supplementing with nutrients found in shrimp. However, the results showed that PL reared on the wet reference shrimp feed still showed superior growth and survival than those reared on a herring feed alone, or supplemented with additives found in shrimp meal (either glucosamine, astaxanthin or both supplements combined). The high survival and growth, low incidence of moulting problems and high availability of waste shrimp material, suggest that non-heat-treated shrimp products are a promising feed ingredient for post-larval European lobsters.

Globally, there is a need for novel vegetarian protein sources. We recently showed that the pH-shift process, using alkaline protein solubilization followed by isoelectric precipitation, is an efficient way to produce extracts with high protein concentrations from Ulva lactuca (>50% on a dry matter basis). However, the total protein yield was low, and to improve this, the effects of adding ulvan lyase, preincubating the seaweed homogenate at pH 8.5 and using different protein extraction temperatures (8 °C, RT and 40 °C), were evaluated in this study. Addition of ulvan lyase reduced protein solubility but increased the precipitation. Incubation at pH 8.5, without ulvan lyase added, significantly increased both protein solubility and precipitation at 8 °C and RT. Temperature per se had no effect on protein solubility, while protein precipitation increased with decreasing temperature. Highest protein yield (29%) was achieved when keeping the process at 8 °C with a preincubation step at pH 8.5 for 1 h. By these process modifications, the yield was 3.2 times higher than achieved by the control process (9.2%).

There is a strong need in animal production for sustainable protein sources used in feed. The aim of the present study was to evaluate the potential of the pH-shift process as a method to concentrate proteins from complex bone-rich herring (Clupea harengus) by-products. By-product parts (frame, head, guts), protein solubilization pH (pH 2.8 or 11.3) and separation g-force (800 or 8000 g) were varied. The findings revealed that protein recovery yields of up to 60% were obtained and that higher protein yield was obtained from the alkaline than the acid process. By-product part and g-force had no significant impact on protein yield. Protein levels reached in the concentrates were 75–80 % (dw basis). Protein concentrates contained a similar amino acid profile as have been reported for fishmeal, with ~40% essential amino acids and up to 7.8% and 2.8% of lysine and methionine. Residual levels of LC n-3 PUFA as well as calcium, magnesium, potassium and phosphorous were also found in the produced protein concentrates which could be an added value. Acid produced concentrates were particularly high in calcium potassium and phosphorous. Provided a careful evaluation, the pH-shift process could become a successful alternative to classic fish meal production for increasing the use of fish by-products for production of protein ingredients for feed.

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.

Earthy off-odour in farm-raised freshwater fish is considered a quality defect. This study aimed to investigate the potential of pH-shift processing to remove off-odours from farm-raised hybrid catfish while at the same time documenting de-novo formation of other volatile compounds. In comparison with crude mince and conventional surimi, the alkali pH-shift process gave larger reductions in geosmin, 2-methylisoborneol, undesirable volatile compounds (e.g. hexanal, (E)-2-nonenal, (E)-2-heptenal, 2-butanone, and hexadecane), lipids, myoglobin, total volatile basic nitrogen, and TCA-soluble peptides (p 0.05). The acid-produced protein isolate showed the highest TBARS and processing-induced evolution of the following volatiles: octanal, nonanal, decanal, 2-butyl-2-octenal, pentadecanal, 1-hexanol, 1-octanol, 1-octen-3-ol, and 2,3-octanediol (p 0.05). Alkali-aided process provided better overall gelling characteristics (i.e. breaking force, deformation, and texture profile) and gave lower fishy, earthy, and rancid off-odour scores (p 0.05). Thus, alkali pH-shift process can be used to isolate gel-forming proteins from hybrid catfish while minimizing the accumulation of undesirable volatile compounds.

Applying value-adding techniques to fish filleting co-products is rendered difficult due to their high susceptibility to lipid oxidation, microbial spoilage, and amine formation. In this study, a recyclable dipping strategy was developed and investigated for its ability to stabilize herring (Clupea harengus) co-products (head, backbone, caudal fin, intestines, belly flap, skin, and in some cases roe) against oxidation and microbial spoilage. From initial screening of seven antioxidative components/formulas in minced herring co-products during ice storage, an oil-soluble rosemary extract (RE-B) and isoascorbic acid (IAA) were identified as most promising candidates. These compounds were then formulated to a recyclable solution to be used for dipping of the herring co-products. The commercial Duralox MANC antioxidant mixture was used as a positive control. Dipping in 0.2% RE-B solution ± 0.5% IAA or in 2% Duralox MANC solutions remarkably increased the oxidation lag phase from 12 days during subsequent storage on ice (0–1 °C) of minced or intact co-products, respectively, even when the antioxidant solutions were re-used up to 10 times. The dipping also reduced microbiological growth and total volatile basic nitrogen, but the effect became weaker with an increased number of re-using cycles. The presented dipping strategies could hereby facilitate more diversified end use of herring co-products from current fish meal to high-quality minces, protein isolates, or oils for the food industry.

Applying value-adding techniques to fish co-products is rendered difficult due to their high susceptibility to hemoglobin (Hb)-mediated lipid oxidation. In this study, we investigated a dipping technology with a solution containing Duralox MANC 213- a mixture of rosemary extract, ascorbic acid, tocopherols and citric acid – to control lipid oxidation during storage at 0 °C and 20 °C. The possibilities to re-use the antioxidant solution was also analyzed, along with studies on the link between Duralox MANC and Hb-form. Dipping in Duralox MANC largely increased the oxidation lag phase; from 3.5 d at 20 °C, and from 11 d at 0 °C. Even after re-use of the solution up to 10 times, lipid oxidation was completely inhibited at 0 °C. Duralox MANC could prevent auto-oxidation and hemin loss of herring Hb; which are suggested as the main mechanisms behind the observed stabilization of herring co-products against lipid oxidation.

Seaweed cultivation and processing industries could contribute to sustainable blue growth and the European bioeconomy. This article contributes a case study evaluation of environmental sustainability of preserved brown seaweed Saccharina latissima by means of environmental life cycle assessment of a pilot facility in Sweden. The study accounts for nutrient bioremediation and carbon capture and includes two alternative hatchery processes, a 2-ha longline cultivation, and four alternative preservation methods (hang-drying outdoors, heated air-cabinet drying, ensiling, and freezing). The study found that as a result of carbon capture and nitrogen and phosphorus uptake (bioremediation) by seaweed, more CO2 and PO4 equivalents are (temporarily) absorbed than emitted by the supply chain. The extent of emissions is most affected by preservation methods undertaken. Impact profiles of the supply chain show that the greatest impact shares result from freezing and air-cabinet drying, both the two most energy-intensive processes, followed by the cultivation infrastructure, highlighting strategic optimization opportunities. Hatchery processes, harvesting, and the low-energy ensilage and hang-drying outdoors were found to have relatively small impact shares. These findings presage the environmentally friendliness of seaweed-based products by documenting their potential to mitigate eutrophication and climate change, even when taking a life cycle perspective.

This study aimed to evaluate the shelf-life of mechanically filleted well-fed Atlantic mackerel during frozen storage at −25 °C and effect of treatment with antioxidants (sodium erythorbate and a polyphosphate mixture) and different antioxidant application methods (dipping, spraying and glazing). Both physicochemical measurements and sensory analysis were applied. Antioxidant treatments prolonged shelf-life of mackerel. Sensory analysis indicated that untreated fillets had a shelf-life of less than 2.5 months, while all antioxidant treated fillets exceeded that. The most effective treatment, dipping fillets into a sodium erythorbate solution, yielding a shelf-life of 15 months. Physicochemical methods used to evaluate degradation of lipids in the fillets were free fatty acids (FFA), lipid hydroperoxides (PV) and thiobarbituric acid reactive substances (TBARS). They did not correlate with sensory results and might therefore be a questionable choice for evaluation of oxidation and development of rancid flavour and odour in complex matrixes such as Atlantic mackerel.

Publisher's version (útgefin grein), This study investigated the efficacy of three commercially relevant packaging methods (vacuum with water glazing VAC-G; vacuum with seawater VAC-S; shatter-layer packaging SL) to improve frozen storage stability of mechanically filleted Atlantic mackerel at − 25 °C, in comparison to water glazing alone (GL) and storage as whole unglazed, block frozen fish. Besides proximate composition and pH of raw material, quality changes were analysed by free fatty acid content (FFA), water holding capacity (WHC), cooking yield, lipid oxidation (lipid hydroperoxides, PV; non-protein bound thiobarbituric acid reactive substances, TBARS) and sensory profiles of cooked samples after 3.5, 8, 10 and 12 months of frozen storage. Vacuum-packaging was effective in mitigating the PV and TBARS as well as rancid odour and flavour. The inclusion of seawater in VAC-S altered the sensory textural attributes of the mackerel fillet to be more juicy, tender and soft and increased the attribute of salty flavour in the sample. SL delayed rancid odour and flavour by 2 months compared to GL. Processing of mackerel under industrial conditions, including filleting, handling, double-freezing and glazing accelerated the formation of FFA as well as losses of WHC and cooking yield in the fillet regardless the packaging methods., Open Access funding provided by Nofima the food research institute. The authors would like to gratefully acknowledge the financial support of Nordic Innovation (MAR14306). Prof. María Guðjónsdóttir at University of Iceland is acknowledged for her valuable feedback on the manuscript.

Nutritional, structural, functional, and sensorial properties of protein isolate developed from salmon (Salmo salar), cod (Gadus morhua), and herring (Clupea harengus) by-products using the pH-shift method was studied. Function of the proteins in an emulsion system in terms of viscoelastic properties was also evaluated. Regardless of origin, the proteins showed satisfying nutritional value as reflected in their high essential amino acid content. The proteins contained significantly (p

peer-reviewed The demand for vegetable proteins increases globally and seaweeds are considered novel and promising protein sources. However, the tough polysaccharide-rich cell walls and the abundance of polyphenols reduce the extractability and digestibility of seaweed proteins. Therefore, food grade, scalable, and environmentally friendly protein extraction techniques are required. To date, little work has been carried out on developing such methods taking into consideration the structural differences between seaweed species. In this work, three different protein extraction methods were applied to three Swedish seaweeds (Porphyra umbilicalis, Ulva lactuca, and Saccharina latissima). These methods included (I) a traditional method using sonication in water and subsequent ammonium sulfate-induced protein precipitation, (II) the pH-shift protein extraction method using alkaline protein solubilization followed by isoelectric precipitation, and (III) the accelerated solvent extraction (ASE®) method where proteins are extracted after pre-removal of lipids and phlorotannins. The highest protein yields were achieved using the pH-shift method applied to P. umbilicalis (22.6 ± 7.3%) and S. latissima (25.1 ± 0.9%). The traditional method resulted in the greatest protein yield when applied to U. lactuca (19.6 ± 0.8%). However, the protein concentration in the produced extracts was highest for all three species using the pH-shift method (71.0 ± 3.7%, 51.2 ± 2.1%, and 40.7 ± 0.5% for P. umbilicalis, U. lactuca, and S. latissima, respectively). In addition, the pH-shift method was found to concentrate the fatty acids in U. lactuca and S. latissima by 2.2 and 1.6 times, respectively. The pH-shift method can therefore be considered a promising strategy for producing seaweed protein ingredients for use in food and feed.

Here we evaluated the levels of lipid oxidation products, fatty acids, ascorbic acid and colour of Porphyra and Ulva after oven-drying at 40 °C, and during subsequent storage for ≥370 days under light, semi-light and dark conditions. Part of the seaweed was pre-soaked in freshwater or pre-coated with a whey protein mixture. Controls consisted of freeze-dried seaweeds. Throughout storage there was a moderate development of the lipid oxidation-derived aldehydes, malondialdehyde, 4-hydroxy-trans-2-hexenal and 4-hydroxy-trans-2-nonenal, while there was a great loss of unsaturated fatty acids and ascorbic acid. Light storage and freeze-drying stimulated the fatty acid loss as well as pigment bleaching, seen as increased a*-values. For Ulva, the coating reduced malondialdehyde, 4-hydroxy-trans-2-hexenal and 4-hydroxy-trans-2-nonenal formation during drying and slightly prevented loss of polyunsaturated fatty acids during light storage. Pre-soaking in freshwater had no effect on the seaweed stability, although it reduced the ash content and thereby increased the relative content of ascorbic acid and fatty acids of the biomasses.

Saccharina latissima biomass cultivated along the Swedish west coast was subjected to four different scalable preservation methods after harvest; freezing, sun-drying, oven-drying and ensiling. Freeze-drying and freezing at −80 °C were also included to provide dry and wet references. The effects of the different preservation methods on the composition of Saccharina biomass (on dry weight, DW, basis), and the recovery as well as properties of high-quality protein, alginate and biogas were evaluated. Sun-drying significantly reduced protein, alginate and fatty acid content of the seaweeds and thereby concentrated ash in the biomass compared to the other methods. Protein/amino acids and fatty acids were significantly concentrated in ensiled biomass, while mannitol and laminarin were reduced compared to the other biomasses. Oven-drying and −20 °C freezing affected the composition the least, with lower ash content and alterations in some specific amino and fatty acids. Sun-drying and ensiling resulted in significantly lower protein solubility at high pH compared to the other biomasses which translated into the lowest total seaweed protein recovery using the pH-shift process. Highest protein yield was obtained with the freeze-dried reference. Ensiling lead to a significant decrease in the molecular weight of alginate, while sun-drying caused a negative effect on alginate by inducing a shift in the guluronic and mannuronic acids composition of alginate. Sun-drying gave the lowest methane yield in the anaerobic digestion experiments while freezing at −80 °C gave the highest yield, closely followed by freezing at −20 °C and ensiling. To conclude, preservation methods must be carefully chosen to protect the valuable component in Saccharina latissima, and to achieve an efficient downstream processing ultimately yielding high quality products as part of a seaweed biorefinery.

This study aimed to evaluate how blending pH-shift produced protein isolates from gutted kilka (Clupeonella cultriventris) and silver carp (Hypophthalmichthys molitrix) affected dynamic rheological and chemical properties of the proteins as well as microstructural and physico-mechanical properties of produced gels. Studied variables were protein solubilization pH (acid vs. alkaline) and blending step (before or after protein precipitation). Comparisons were made with conventionally washed minces from kilka and silver carp fillets; either alone or after blending. Rheological studies revealed that blending alkali-produced protein isolates before precipitation resulted in rapid increase of G' reflecting the formation of intermolecular protein-protein interactions with higher rate. Furthermore, blending of alkali-produced protein isolates and washed minces, respectively, of kilka and silver carp improved physico-mechanical properties of the resultant gels compared to pure kilka proteins. However, the pH-shift method showed higher efficacy in development of blend surimi at the same blending ratio compared to the conventional washing.

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.

Flocculation and sedimentation of a protein-rich biomass from shrimp boiling water (SBW) using food grade polysaccharides (carrageenan, alginate and carboxymethyl cellulose (CMC)) as flocculants was investigated at different pH-values. The effect of flocculant concentration on particle size and viscosity of SBW was also evaluated. Flocculation with carrageenan (0.45 g/L) at pH = 4 exhibited the most efficient protein sedimentation; protein concentration of the upper phase was here reduced by 77%, allowing 86% protein to be sedimented from SBW. Flocculation by alginate and CMC at pH = 4 showed 67% and 60% protein reduction of the upper phase at concentrations of 0.5 and 0.2 g/L, respectively. Contrary to alginate and CMC, carrageenan concentration affected the size distribution of flocs. Finally, carrageenan at 0.45 g/L and pH = 4 was successfully tested in a scaled up trial (5L) providing 78.5% protein recovery and a biomass with 75% protein on dry weight basis.

In the light of the global search for novel and sustainable protein sources, macroalgal proteins are becoming an attractive target. To date, mainly red and green macroalgae have been investigated in this respect, whereas the brown species are less studied, possibly because of the lower content of protein. In a biorefinery context, however, the protein content of brown macroalgae can still be economically interesting due to fast growth and the possibility to co-extract other compounds, such as alginates. The aim of this study was to develop a simple, scalable pH shift-based protein isolation technique applicable on wet Saccharina latissima biomass. Factors investigated were extraction volume, temperature, protein solubilization pH, osmoshock pretreatment and protein precipitation pH. Maximum protein solubility was obtained at pH 12, where 34 % of the total protein content could be extracted with 5.56 volumes of extraction solution (20 volumes on dry weight (dw) basis). Osmoshocking significantly increased the yield, and 20, 40 and 60 volumes of water (dw basis) gave 45.1, 46.8 and 59.5 % yield, respectively. The temperature during osmoshocking did not significantly affect the extraction yield, and extended time (16 vs. 1 or 2 h) reduced protein yield. Precipitation of solubilized proteins was possible below pH 4; the highest precipitation yield, 34.5 %, was obtained at pH 2. After combined alkaline extraction and acid precipitation, 16.01 % of the Saccharina proteins were recovered, which can be considered acceptable in comparison to other studies on algae but leaves some room for improvement when compared to protein extraction from, for instance, soy.

This study monitored the biomass composition of Saccharina latissima during a potential harvesting season on the West coast of Sweden, in order to find suitable harvest times for biorefinery purposes. Specimens of S. latissima were sampled at three locations in June, August and October and the biomass was analysed for its macromolecular composition, as well as for the content of several specific compounds, e.g. sugars and fatty acids. PERMANOVA analyses showed that there was a significant difference in the biomass composition among time points. The total carbohydrate concentration was lowest in June and peaked at 360 mg g-1 dry weight in August, while the mannitol content was highest, 90 mg g-1, in June and decreased throughout the sampling period. Total protein and fatty acid concentrations were found to be approximately 80 and 3 mg g-1, respectively, with relatively little variation over time. Overall, there was little spatial variation in the macromolecular composition, although the concentration of some specific monosaccharides and fatty acids, as well as the total phenolic content, differed among localities. We discuss the implications of the observed variation in biomass composition of S. latissima for future biorefinery purposes.

To allow value adding into foods, stabilizing strategies for fish by-products are needed based on their high susceptibility to hemoglobin (Hb)-mediated lipid oxidation. Here, three strategies for preventing lipid oxidation in herring (Clupea harengus) by-products during ice-storage were studied: (i) rinsing away Hb with water or 0.9% NaCl with/without antioxidants (Duralox-MANC, erythorbate and ethylenediamine-tetraacetic acid (EDTA)), (ii) incubation in water/0.9% NaCl with/without antioxidants, (iii) mincing with subsequent addition of the mentioned antioxidants. Only 10–18% Hb was rinsed away in (i), and the effect of this rinsing on peroxide value (PV) or TBA-reactive substances (TBARS) development was limited. Rinsing or incubating by-products in antioxidant solutions however significantly (p ≤ 0.05) increased shelf life from 12 days; Duralox-MANC was particularly efficient. The presented strategies could hereby facilitate more diversified end-use of herring by-products from being 100% feed, to include also high-quality minces, protein isolates or oils for the food industry.

Quality changes of vacuum-packed Atlantic mackerel (Scomber scombrus) fillets during 12 months’ frozen storage at −27°C and 9 days’ chilled storage at +4°C were evaluated. Freezing at −27°C preserved the long chain n-3 polyunsaturated fatty acids (LC n-3 PUFAs), both in light and dark muscle, vitamin D, and the low molecular weight metabolites (LMW) (studied by high resolution nuclear magnetic resonance spectroscopy, HR NMR). Protein oxidation took place, especially between 1 and 7 months, decreasing water holding capacity and protein extractability. During chilled storage, no lipid or protein oxidation was observed, but lipolysis increased, and several LMW metabolites relevant for sensory and nutritional quality degraded into non-favorable compounds. The content of biogenic amines was high at day 9 (e.g., 18 mg histamine/100 g), jeopardizing safety. Preservation of mackerel fillets by freezing at −27°C is thus a better option compared to prolonged chilled storage at +4°C; the quality was well preserved for 12 months’ frozen storage. Locked until 16.2.2019 due to copyright restrictions. This is an [Accepted Manuscript] of an article published by Taylor & Francis in [Journal of Aquatic Food Product Technology] on [16 Feb 2018], available at https://doi.org/10.1080/10498850.2018.1436107

In vitro digestion of marine oils has been reported to promote lipid oxidation, including the formation of reactive aldehydes (e.g., malondialdehyde (MDA) and 4-hydroxy-2-hexenal (HHE)). We aimed to investigate if human in vitro digestion of supplemental levels of oils from algae, cod liver, and krill, in addition to pure MDA and HHE, affect intestinal Caco-2 cell survival and oxidative stress. Cell viability was not significantly affected by the digests of marine oils or by pure MDA and HHE (0–90 μM). Cellular levels of HSP-70, a chaperone involved in the prevention of stress-induced protein unfolding was significantly decreased (14%, 28%, and 14% of control for algae, cod and krill oil, respectively; p ≤ 0.05). The oxidoreductase thioredoxin-1 (Trx-1) involved in reducing oxidative stress was also lower after incubation with the digested oils (26%, 53%, and 22% of control for algae, cod, and krill oil, respectively; p ≤ 0.001). The aldehydes MDA and HHE did not affect HSP-70 or Trx-1 at low levels (8.3 and 1.4 μM, respectively), whilst a mixture of MDA and HHE lowered Trx-1 at high levels (45 μM), indicating less exposure to oxidative stress. We conclude that human digests of the investigated marine oils and their content of MDA and HHE did not cause a stress response in human intestinal Caco-2 cells.

Four types of herring industry processing waters; refrigerated sea water (RSW), storage water (SW), processing water from cutting (PW) and pre-salting brines (SB) were subjected to chemical characterization and biomolecule recovery using electroflocculation (EF) and ultrafiltration (UF). The highest protein and fatty acid content were found in SB's, up to 12.7 ± 0.3 and 2.5 ± 0.1 g L−1, respectively. Long chain n-3 polyunsaturated fatty acids represented up to 44.5% of total fatty acids. In all samples, leucine and glutamic acid/glutamine were the dominating amino acids while calcium and magnesium were the dominating trace elements. EF plus UF in series recovered up to 80% proteins and fatty acids from SB's and reduced chemical oxygen demand by 70%. Foaming and emulsifying properties of biomolecules were improved or unaffected by EF/UF treatment. To conclude, large amounts of biomass are currently lost per ton of processed herring, e.g. ∼9.2 kg proteins and ∼4.1 kg fatty acids; EF/UF represents a promising way of turning such losses to a potential income.

Fractionation of plant and animal raw materials by pH-shift processing has been widely applied to purify proteins. The principle is to solubilize proteins at high or low pH, removing debris and precipitating the proteins near their isoelectric point. We here describe the pH-shift process on commercially available Nannochloropsis oculata. The partitioning of major nutrients into the various fractions of the process was studied. Proteins were found to exhibit maximal solubility between pH7 and 10, with a minimal solubility below pH4. Two process versions were investigated in this study, with solubilization at either pH7 (native pH) or 10; both versions were precipitated at pH3. Up to 85% of both the protein and total fatty acids were recovered in the final product, compared to the initial algal slurry. Protein, total fatty acids and carbohydrates were concentrated in the final product, while the ash content was lower compared to the starting material. From a processing point of view, solubilization of Nannochloropsis at native pH was found to be preferable, since less chemicals were consumed compared to high-pH solubilization. Owing to its content of protein and (total) fatty acids (23 and 12% of dry weight, respectively), the latter enriched in eicosapentaenoic acid (EPA), the product of the pH-shift process has potential as a functional food ingredient.

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

Collagen and collagen hydrolysate (CH) was recovered from the bone and skin containing sediment residue emerging during pH-shift-based protein isolation from silver carp. Hydrolysis resulted in higher yield (15.1–15.4%) compared to collagen isolation by acid or pepsin (3.1–5.9%) (p < 0.05). Isolated collagens were characterized as type I and maintained their triple-helical structure, confirmed by SDS-PAGE and FTIR. Pepsin-hydrolysis and sequential hydrolysis by pepsin and trypsin hydrolyzed all heavy molecular weight chains of collagen but sequential hydrolysis yielded higher degree of hydrolysis. When CH was added to a silver carp protein isolate prior to gelation, the gel behavior was dependent on molecular weight of the added CH. More hydrolyzed collagen emerging from sequential hydrolysis improved water holding capacity of the gel while reducing its breaking force. Thus, residue from pH-shift processing of fish can be used for isolation of high quality collagen/CH and provides a promising basis for a multiple-product fish biorefinery.

Bioaktivnost hidrolizata proteina iz mesa bakalara (Gadus morhua) i kokoši (Gallus domesticus) prije i nakon in vitro gastrointestinalne (GI) probave istražena je pomoću kvasca Saccharomyces cerevisiae kao modelnog organizma. Kako bi simulirali uvjete probave u ljudskom organizmu i istražili utjecaj modulacije GI sustava na stanični odgovor, oba hidrolizata su prije dodavanja stanicama bila izložena GI probavi in vitro. Istražen je učinak neprobavljenih i probavljenih hidrolizata na unutarstaničnu oksidaciju, staničnu metaboličku energiju i proteom. Između proteinskih hidrolizata dobivenih iz mesa bakalara i kokoši nisu utvrđene razlike u antioksidacijskom učinku. Veća antioksidacijka aktivnost utvrđena je kod probavljenih hidrolizata, pri čemu je vrijednost unutarstanične oksidacije u mesu bakalara iznosila (70,20,8) %, a u mesu kokoši (74,51,4) %, dok su kod neprobavljenih hidrolizata te vrijednosti iznosile (95,51,2) % u mesu bakalara te (90,50,7) % u mesu kokoši. Izvor proteinskog hidrolizata kao i probava nisu imali nikakvog utjecaja na staničnu metaboličku energiju. Na razini proteoma, probavljeni hidrolizati su imali bitno jači učinak na odgovor stanica nego njihovi neprobavljeni ekvivalenti; također, peptidi iz mesa bakalara utjecali su nešto više na stanični odgovor nego peptidi iz mesa kokoši. Poznavanje djelovanja proteinskih hidrolizata iz hrane te njihove probave u živim stanicama, kao i na razini proteoma, važno je za daljnje vrednovanje njihove aktivnosti u višim eukariotima, a radi razvoja novih proizvoda, što bi u ovom slučaju bili peptidi dobiveni iz mesa bakalara i kokoši koji se mogu upotrijebiti kao funkcionalni sastojci., Bioactivity of cod (Gadus morhua) and chicken (Gallus domesticus) protein hydrolysates before and after in vitro gastrointestinal (GI) digestion was investigated using yeast Saccharomyces cerevisiae as a model organism. Both hydrolysates were exposed to in vitro GI digestion prior to cellular exposure to simulate digestion conditions in the human body and therefore investigate the role of modulations in the GI tract on the cell response. The effect of digested and undigested hydrolysates on intracellular oxidation, cellular metabolic energy and proteome level was investigated. No difference in the effect on intracellular oxidation activity was obtained between cod and chicken hydrolysates, while higher affect on intracellular oxidation was provided by digested hydrolysates, with relative values of intracellular oxidation of cod of (70.2±0.8) and chicken of (74.5±1.4) % than by undigested ones, where values of cod and chicken were (95.5±1.2) and (90.5±0.7) %, respectively. Neither species nor digestion had any effect on cellular metabolic energy. At proteome level, digested hydrolysates gave again significantly stronger responses than undigested counterparts; cod peptides here also gave somewhat stronger response than chicken peptides. The knowledge of the action of food protein hydrolysates and their digests within live cells, also at proteome level, is important for further validation of their activity in higher eukaryotes to develop new functional food ingredients, such as in this case chicken and cod muscle-derived peptides.

Determination of microalgaes’ fatty acid content is often done with chloroform and methanol according to the Bligh and Dyer extraction, though faster methods exist. A number of comparisons between the Bligh and Dyer and faster methods have resulted in contradicting data, possibly due to differences in algae used and the different versions of the Bligh and Dyer method applied. Here, various forms of direct-transesterification (D-TE) and two-step transesterification (2-TE), including three versions developed in our lab, are compared with the original Bligh and Dyer (Can J Biochem Physiol 37: 911–917, 1959) extraction and two modifications thereof (Lee et al. J AOAC Int 79:487–492, 1996, and our own acidified version) on microalgae with different cell walls: Isochrysis galbana, Nannochloropsis oculata, and Phaeodactylum tricornutum. In total, fatty acid extracts from 11 methods were separated and quantified by gas chromatography with mass spectrometry. Results show that, for N. oculata and P. tricornutum, methods based on chloroform–methanol underestimated the fatty acid content compared with the 2-TE and D-TE methods, which gave similar results. Moreover, D-TE methods are faster than chloroform–methanol methods and use chemicals that are less toxic. Of the D-TE methods, the ones using hydrochloric acid and sulfuric acid recovered the most fatty acids, while boron trifluoride recovered slightly less. The main qualitative difference between the fatty acids recovered was that the chloroform–methanol methods recovered less saturated fatty acids in P. tricornutum. Electronic supplementary material The online version of this article (doi:10.1007/s00216-014-8155-3) contains supplementary material, which is available to authorized users.

Electrostatic interactions between haemoglobin (Hb) and muscle components of fish may be an initial step of Hb-mediated lipid oxidation. This mechanism was investigated by examining the interaction of anionic HbIV and cationic Hbl with insoluble components of washed cod mince under different pH and salt conditions. Lipid oxidation was monitored in parallel using the thiobarbituric acid reactive substances (TBARS) test. Higher binding of Hbl to washed cod mince occurred compared to HbIV, yet HbIV better promoted lipid oxidation. An increase in pH from 5.7 to 6.3 and further to 7.0 lowered both Hb-binding and TBARS development. Addition of NaCl decreased Hb-binding but still did not influence Hb-mediated lipid oxidation. Thus, Hb binding had no consistent effect on lipid oxidation of washed cod mince. Rapid haemin release from the anionic Hb appeared to be a primary facilitator of lipid oxidation, overshadowing the greater binding ability of the cationic Hb. (C) 2013 Elsevier Ltd. All rights reserved.

The aim of the present study was to investigate whether the following four markers: vitamin B12, selenium, vitamin D, and parvalbumin may be used as compliance markers for fish intake.Blood samples from a randomized cross-over herring intervention study (n = 32) were analysed by HPLC and immunochemistry. The criteria were that plasma or serum concentrations of candidate compliance markers after the herring diet should increase significantly compared to starting concentrations. In addition, the reference meat diet should not yield an increase in plasma concentration of the candidate marker.Vitamin B12 and selenium met the set criteria for indicating a correlation between the marker and fish intake with significant increases in serum concentrations at 8.9% (p = 0.008) and 4.6% (p = 0.02), respectively, after a 6-week herring intervention (5 meals a week). Parvalbumin and 25-hydroxy vitamin D3 levels did not increase significantly after the herring interventions.Vitamin B12 may be suitable as a compliance marker for fish intake. Although selenium also met the criteria, the change in selenium serum concentrations was small compared to the change in vitamin B12 levels.

SCOPE: What effect does replacing chicken or pork with herring as the main dietary source of protein have on the human plasma metabolome? METHOD AND RESULTS: A randomised crossover trial with 15 healthy obese men and women (age 24-70 years). Subjects were randomly assigned to four weeks of herring diet or a reference diet of chicken and lean pork, five meals per week, followed by a washout and the other intervention arm. Fasting blood serum metabolites were analysed at 0, 2 and 4 weeks for eleven subjects with available samples, using GC-MS based metabolomics. The herring diet decreased plasma citrate, fumarate, isocitrate, glycolate, oxalate, agmatine and methyhistidine and increased asparagine, ornithine, glutamine and the hexosamine glucosamine. Modelling found that the tricarboxylic acid cycle, glyoxylate, and arginine metabolism were affected by the intervention. The effect on arginine metabolism was supported by an increase in blood nitric oxide in males on the herring diet. CONCLUSION: The results suggest that eating herring instead of chicken and lean pork leads to important metabolic effects, particularly on energy and amino acid metabolism. Our findings support the hypothesis that there are metabolic effects of herring intake unrelated to the long chain n-3 polyunsaturated fatty acid content.

The pH-shift process fractionates biomass into soluble proteins and insoluble fractions, followed by precipitation and recovery of the solubilized proteins. Nannochloropsis oculata in seawater was subjected to the pH-shift process, followed by digestion of various intermediates and product fractions of the process, using the Infogest in vitro digestion model (Minekus et al., 2014) with added gastric lipase. As measures for protein and lipid accessibility, degrees of protein hydrolysis and fatty acid liberation were assessed post-digestion and compared to the amounts of peptide bonds and total fatty acids present in the raw materials. Results showed that neither proteins nor lipids of intact Nannochloropsis cells were accessible to the mammalian digestive enzymes used in the digestion model. Cell disruption, and to a lesser extent, further pH-shift processing with protein solubilisation at pH 7 or pH 10, increased the accessibility of lipids. For proteins, differences amongst the pH-shift processed materials were non-significant, though pre-freezing the product prior to digestion increased the accessibility from 32% to 47%. For fatty acids, pH-shift process-products gave rise to 43% to 52% lipolysis, with higher lipolysis for products solubilised at pH 10 as opposed to pH 7. Our results indicate the importance of processing to produce an algal product that has beneficial nutritional properties when applied as food or feed.

Marine lipids contain a high proportion of polyunsaturated fatty acids (PUFA), including the characteristic long chain (LC) n-3 PUFA. Upon peroxidation these lipids generate reactive products, such as malondialdehyde (MDA), 4-hydroxy-2-hexenal (HHE) and 4-hydroxy-2-nonenal (HNE), which can form covalent adducts with biomolecules and thus are regarded as genotoxic and cytotoxic. PUFA peroxidation can occur both before and after ingestion. The aim of this study was to determine what levels of MDA, HHE and HNE can evolve in the gastric and intestinal lumen after ingesting meals containing fish or fish oil using a dynamic gastrointestinal (GI) model (TIM). The impact of the fish muscle matrix, lipid content, fish species, and oven baking on GI oxidation was evaluated. MDA and HHE concentrations in gastric lumen increased for all meals during digestion, with the highest level found with herring mince; ∼25 μM MDA and ∼850 nM HHE. Aldehyde concentrations reached in intestinal lumen during digestion of fish containing meals were generally lower than in gastric lumen, while isolated herring oils (bulk and emulsified) generated higher MDA and HHE values in intestinal lumen compared to gastric lumen. Based on aldehyde levels in gastric lumen, meals containing herring lipids were ranked: raw herring (17% lipid) = baked herring (4% lipid) > raw herring (4% lipid) ≫ herring oil emulsion > herring oil. Herring developed higher concentrations of MDA and HHE during gastric digestion compared to salmon, which initially contained lower levels of oxidation products. Cooked salmon generated higher MDA concentrations during digestion than raw salmon. Low levels of HNE were observed during digestion of all test meals, in accordance with the low content of n-6 PUFA in fish lipids.

Previous studies of the pH-shift protein isolation process have shown that substantial amounts of solubilized proteins can be trapped in the sediments formed in the first centrifugation step of this process. As a strategy to improve the protein yield during pH-shift processing, the aim of this study was to evaluate how filtration as an alternative to centrifugation in the first separation step of pH-shift processing of blue whiting affected proteins yield and protein isolate characteristics (basic composition, polypeptide profiles, surimi gel quality and color attributes). The study comprised both the acid and alkaline versions of the method, and also fresh as well as frozen fish raw material. Results showed that the replacement of centrifugation with filtration substantially improved the protein yield by from about 38% to 62%, but also reduced the removal of lipid. There were no significant effects on gel quality. Protein isolates from fresh raw material were about 5 % whiter and frozen raw materials about 3% whiter with centrifugation as compared to filtration in the pHshift process. For surimi from fresh raw material centrifugation gave about 2 % whiter gels, while the gels from frozen raw material were about 3% whiter for filtered compared to centrifuged material. The whitest isolates and gels were obtained with acid processing of fresh blue whiting. Slight proteolytic breakdown resulting in fragments of 83 and 152 kDa was however noted with the acid process, especially when centrifugation was used.

Herring ( Clupea harengus ) and other pelagic fish species are mainly used for fish meal and oil production and not for human consumption. In this study, acid pH-shift processing and alkaline pH-shift processing were used to isolate proteins from whole gutted herring with the aim to investigate the potential use of herring proteins as a food ingredient. The acid and alkaline processes gave rise to similar protein yields, 59.3 and 57.3%. The protein isolates from both processes had a significantly (p0.05) whiter color and higher protein and lower lipid contents than the starting material. The removal of ash was80% for both processes, with a trend (p = 0.07) toward higher removal during the alkaline process. Also, Ca and Mg removal was significantly (p0.05) higher during the alkaline process. The isolated proteins from the acid process contained myosin degradation products and had a lower salt solubility than proteins from the alkaline process. Both protein isolates had an amino acid profile meeting the recommendations for adults according to FAO/WHO/UNU and could produce a surimi gel of medium strength. The results show that pH-shift processing could be a valuable method for the production of functional food proteins from gutted herring.

Dioxins and PCBs are toxic, lipophilic, and persistent substances that impose a serious health threat. A major risk of exposure to these toxic substances is consumption of fish from polluted waters, such as the Baltic Sea. The aim of this study was to investigate if pH-shift processing of Baltic herring with elevated toxicity levels could be used to produce a protein isolate with low fat content and, thereby, reduced dioxin and PCB levels. Both acid (pH 2.7) and alkaline (pH 11.2) pH-shift processing were investigated and resulted in efficient reduction of fat, dioxin, and PCB levels. A reduction of 70-80% per amount of protein was determined for all of these parameters. The amounts, and thus the removal, of lipids and dioxins (R(2) = 0.952) as well as lipids and PCBs (R(2) = 0.996) were highly correlated (p < 0.01). A mass balance of the alkaline pH-shift process showed that most of the fat and pollutants were found in the floating fat emulsion layer of the first centrifugation, followed by the pellet of the first centrifugation. These data show that the pH-shift protein isolation technique can be used to process herring with elevated dioxin and PCB levels and thereby increase the usage possibilities of such fish.

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.

The acid and alkaline solubilization processes for isolating muscle protein from ground fish raw materials are investigated by scrutinizing the literature. Following an introduction to the processes, with some underlying chemistry, patents related to the acid and alkaline solubilization process are described together with previously patented methods for processing of protein isolates. Focus is then placed on comparing a range of factors important in fish muscle protein isolation between the acid and alkaline solubilization processes, and classic washing-based surimi technology. The factors addressed were: protein yield, gel quality, color, lipid reduction, lipid oxidation, microbial stability, and frozen storage stability. A long series of studies made with different fish/shellfish species have been used for this purpose. Certain results are summarized in table form (protein yields, gel strength, and whiteness), others only in text form. From this part of the review, it is obvious that the acid process often has certain advantages (e.g., protein yield) and the alkaline process other ones (gel strength, whiteness, lipid removal, lipid oxidation, and total microbial count). Thus, the choice of method depends on the application. It is clear that most species respond differently to acid and alkaline solubilization, which is why the two methods are initially compared. In a section about new processing attempts, the use of the acid and alkaline methodology for isolating proteins from whole fish/shellfish and fish by-products is reviewed together with attempts to recover waste water proteins and attempts to modify the process. Tentative uses of the new protein isolates, e.g., as coatings, protein brines, and emulsifiers are finally described together with some conclusions and future opportunities for the acid and alkaline processes.

The aqueous fraction (press juice, PJ) from herring muscle was recently shown to inhibit hemoglobin-mediated oxidation of washed fish mince lipids during ice storage. As a first step to evaluate potential in vivo antioxidative effects from herring PJ, the aim of this study was to investigate whether herring PJ retains its antioxidative capacity during a simulated gastrointestinal (GI) digestion. Press juice from whole muscle (WMPJ) and light muscle (LMPJ) was mixed with pepsin solution followed by stepwise pH adjustments and additions of pancreatin and bile solutions. Digestive enzymes were removed from samples by ultrafiltration (10 kDa). Before, during, and after digestion, samples were analyzed for their peptide content and for antioxidative properties with the oxygen radical absorbance capacity (ORAC) and the low-density lipoprotein (LDL) oxidation assays. From 0 to 165 min of digestion, the content of10 kDa peptides in WMPJ and LMPJ samples increased 12- and 7-fold, respectively. Further, both samples got approximately 12.5 times higher ORAC values and gave rise to approximately 1.3-fold increased lag phase in Cu2+-induced LDL oxidation. The largest changes in peptide content, ORAC values, and LDL oxidation inhibition occurred between 30 and 75 min of digestion, indicating that these parameters might be interrelated. When comparing analytical data obtained after 165 min of digestion with data obtained from analyses of native nondigested PJs, it was found that the data on peptide content, ORAC, and LDL oxidation from digested PJs were 64-69%, 121-161%, and 112-115%, respectively, of those of nondigested PJs. The study thus showed that enzymatic breakdown of PJ proteins under GI-like conditions increases the peroxyl radical scavenging activity and the potential to inhibit LDL oxidation of herring PJs. These data provide a solid basis for further studies of uptake and in vivo activities of herring-derived aqueous antioxidants.

Objective: To assess the effect of a 4-week herring diet compared to a reference diet on biomarkers for cardiovascular disease in obese subjects. Design: Randomized crossover trial. Setting: Department of Internal Medicine, Sahlgrenska University Hospital. Subjects: Fifteen healthy obese men and women ( age 24-70 years) included, 13 completed. Intervention: Subjects were randomly assigned to four weeks of herring diet ( 150 g baked herring fillets/day 5, days/week) or reference diet ( pork and chicken fillets) and switched diets after 2 weeks washout. P-total cholesterol, p-TAG, p-HDL, p-HDL(2), p-HDL(3), p-LDL, p-apolipoprotein A, p-apolipoprotein B, p-Lipoprotein ( a), p-fibrinogen, p-C- reactive protein and p-antioxidative capacity were analysed at 0,2,4,6,8 and 10 weeks. Results: P-HDL was significantly higher after the herring diet period compared to after the reference diet period; 1.22 vs 1.13 mmol/l ( P = 0.036). There was a small, but not statistically significant, decrease in TAG but no effect on other biomarkers. TEAC and FRAP, but not ORAC-values, indicated that plasma antioxidants may have been reduced. CRP tended to be lower after the herring diet compared to after the reference diet. Conclusions: Consumption of oven-baked herring ( 150g/day, 5 days/week) for 4 weeks, compared to consumption of pork and chicken fillets, significantly increased p-HDL. Patients with insulin resistance and obesity, who commonly have low HDL, may therefore benefit from addition of herring to the diet.

This study aimed at unravelling the antioxidative capacity of low molecular weight compounds (LMWC) (peptides, amino acids and phenolic acids) present in salt brines from the marinated herring production. Brines were fractionated into

Microalgae have great prospects as a sustainable resource of lipids for refinement into nutraceuticals and biodiesel, which increases the need for detailed insights into their intracellular lipid synthesis/storage mechanisms. As an alternative strategy to solvent- and label-based lipid quantification techniques, we introduce time-gated coherent anti-Stokes Raman scattering (CARS) microscopy for monitoring lipid contents in living algae, despite strong autofluorescence from the chloroplasts, at approximately picogram and subcellular levels by probing inherent molecular vibrations. Intracellular lipid droplet synthesis was followed in Phaeodactylum tricornutum algae grown under (1) light/nutrient-replete (control [Ctrl]), (2) light-limited (LL), and (3) nitrogen-starved (NS) conditions. Good correlation (r 2 = 0.924) was found between lipid volume data yielded by CARS microscopy and total fatty acid content obtained from gas chromatography-mass spectrometry analysis. In Ctrl and LL cells, micron-sized lipid droplets were found to increase in number throughout the growth phases, particularly in the stationary phase. During more excessive lipid accumulation, as observed in NS cells, promising commercial harvest as biofuels and nutritional lipids, several micron-sized droplets were present already initially during cultivation, which then fused into a single giant droplet toward stationary phase alongside with new droplets emerging. CARS microspectroscopy further indicated lower lipid fluidity in NS cells than in Ctrl and LL cells, potentially due to higher fatty acid saturation. This agreed with the fatty acid profiles gathered by gas chromatography-mass spectrometry. CARS microscopy could thus provide quantitative and semiqualitative data at the single-cell level along with important insights into lipid-accumulating mechanisms, here revealing two different modes for normal and excessive lipid accumulation.