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Liquid loss (i.e. loss of water and liquid fat) is an important property for salmonids when evaluating fish quality in production and as final product. It can be measured by several means, for example by liquid leakage or by liquid holding capacity. The present study examines how liquid leakage and liquid holding capacity of salmon and trout are influenced by fat content. Liquid leakage did not depend on fat content whereas the liquid holding capacity was lower for fish with high fat content. Thus the methods provide supplementary rather than equal information. Furthermore the water loss part was linear depending on liquid loss. The results indicate that fat is more loosely bound in trout than in salmon. These findings may be of immediate relevance to quality control of high-value fat fish products, to assessment of raw material properties, to an efficient treatment in the production and to process control.

This study aimed to characterise peptide fractions (>5 kDa, 3–5 kDa and <3 kDa) with antioxidative activity obtained from a cod protein hydrolysate. The free amino acids in all fractions were dominated by Ala, Gly, Glu and Ser. The total amino acid composition had high proportions of Lys, Ala and Glu. The 3–5 kDa and <3 kDa fractions were further fractionated by size exclusion chromatography. All sub-fractions showed high Fe2+ chelating activity. The DPPH radical-scavenging activity of the 3–5 kDa fraction was exerted mainly by one sub-fraction dominated by peptides with masses below 600 Da. The DPPH radical-scavenging activity of the <3 kDa fraction was exerted by sub-fractions with low molecular weight. The highest reducing power was found in a sub-fraction containing peptides rich in Arg, Tyr and Phe. Both free amino acids and low molecular weight peptides thus seemed to contribute to the antioxidative activity of the peptide fractions, and Tyr seemed to play a major role in the antioxidant activity.

The aim of this work was to study whether the type of protein and lipid source in feed for organic Rainbow trout (Onchorhynchus mykiss) influenced the sensory quality. The protein sources were fishmeal and a matrix of organic vegetable plant mealsproteins, while the lipid sources were fish oil and organic oils of linseed, sunflower, rapeseed and grape seed, respectively. Sensory profiling was performed after 3, 5, 7 and 14 days of storage in ice. Besides sensory analysis also lipid profiles weare measured. The resultsed showed that the lipid type in the feed aeffected the sensory characteristics after 3 days of storage. Especially the trout that had grape seed oil in the feed had a different sensory profile than the trout that had fish oil in the feed. These differences could be explained by the lipid profiles in the fillets. Also after 7 days of ice storage differences in the sensory profile wereas observed again as a result of the used lipid types used. After 7 days of ice storage ThusHere the trout that had grape seed oil orand rapeseed oil for instance had a more neutral flavor and odor profile compared to the other trout fed on linseed or sunflower oil´s. After 14 days of storage no effect of lipid type in the feed was observed, but the trout which had fish meal as protein source had higher intensity of several negative sensory descriptors compared to trout that had the vegetable protein matrix. Overall the results showed that the dietaryfeeds content of protein and lipid aeffecteds the sensory characteristics of the trout in different ways during the ice storage period.

There is an interest in bioprospecting organisms from the aquatic environment to find novel bioactive compounds with health promoting or other functional properties. The aim of this study was to evaluate extracts from untreated and heat-treated salmon tissues for their radical scavenging activities and for their ability to inhibit activity of the proteases angiotensin I-converting enzyme (ACE) and dipeptidyl peptidase 4 (DPP-4). In vitro assays were used to detect these activities and the corresponding candidate bioactive compounds were characterized by LC-MS/MS.Radical scavenging activity was detected in <10kDa extracts of gills, belly flap muscle and skin with EC50 values of 39, 82 and 100 µg/mL, respectively. No ACE or DPP-4 inhibiting activity could be detected. LC-MS/MS analysis of dominating compounds in active fractions from size exclusion chromatography showed that families of related compounds were found in several fractions from different tissues but most pronounced in gills. One family was defined according to content of a specific amino acid sequence (PW). Three families were defined by the m/z value of the smallest compound reported in each family (219, 434 and 403). The three latter families did not contain standard unmodified amino acids, indicating peptides with modified amino acids or other kinds of molecules.Industrial relevance. Bioprospecting in fish tissue traditionally regarded as waste can lead to detection of novel natural bioactive compounds including peptides, which could have nutritional, pharmaceutical or other functional value and be used in health and functional foods, thus increasing the value adding of secondary marine products. A number of naturally occurring antimicrobial peptides have been characterized from fish skin and gills, such as piscidins, but these and other fish tissues may contain numerous other compounds with bioactive properties. Such compounds could be extracted by the subsection of the fish industry that processes

Brines generated during the last marination step in the production of marinated herring (Clupea harengus) were chemically characterized and analyzed for antioxidant and enzyme activities. The end-products were vinegar cured, spice cured and traditional barrel-salted herring with either salt or spices. The chemical characterization encompassed pH, dry matter, ash, salt, fatty acids, protein, polypeptide pattern, iron and nitrogen. The antioxidant activity was tested with three assays measuring: iron chelation, reducing power and radical scavenging activity. The enzymatic activity for peroxidase and protease were also tested. Results revealed that the brine can contain up to 56.7 mg protein/ mL, up to 20.1 mg fatty acid/mL, good antioxidant activity, high amounts of the antioxidative amino acids lysine, alanine, and glycine, and high enzymatic activity. The potential of using the protein-rich fraction with biological activity from brines from the marinated herring production was demonstrated in this work.

Recently, fish meal and fish oil have increasingly been replaced with proteins and oils from vegetable sources in the diets of farmed salmonids, but the consequences for the oxidative stability of the resulting fish products have only been investigated to a limited extent. This presentation will discuss results from two recent studies from our laboratory on this topic. In the first study, rainbow trout were fed six different diets, which differed in the ratio between marine oil and proteins vs. vegetable oil and protein. Rapeseed oil was used as the oil source and the vegetable proteins were a mix based on pea, wheat, sunflower and beans. In the second study, one group of rainbow trout was fed a traditional diet based on fish meal and fish oil, whereas the other five groups were fed diets in which 40 % of the fish meal was replaced with plant proteins from peas, horse bean and rapeseed. The oil source was either fish oil, linseed oil, sunflower oil, rapeseed oil or grapeseed oil. Rainbow trout was stored on ice for up to 14 days. In both studies, the effect of the feeding regime on the fatty acid composition and lipid oxidation in the fish fillet was determined. In the first study, the effect of the diet on protein oxidation in fish fillets was also determined. In both studies, feeding regimes significantly influenced fatty acid composition. Moreover concentration of primary oxidation products at the end of the storage period was highest in fish fed lipids with the highest unsaturation index and lowest in fish fed with lipids with low unsaturation index. The effect of the diet on secondary oxidation products differed between different types of volatiles. There were no clear effects of diets on protein oxidation, but data indicated that compounds present in the marine ingredients might have had an effect on protein oxidation.

The aim of this study was to screen different protein hydrolysates with respect to their antioxidative properties in order to select the most promising extracts for further evaluation in oil-in-water emulsions. Three fractions of protein hydrolysates (Crude, >5kDa and 5kDa, 3-5kDa and

The aim of this work was to study which effects protein and lipid source in feed for organic rainbow trout (Oncohynchus mykiss) may have on the sensory quality of the final product after up to 14 days of storage in ice. The protein sources used in the experiment were fishmeal and a mixture of vegetable protein. While the lipid sources were fish, linseed, sunflower, rapeseed and grape seed oil. After slaughtering all fish were frozen (-40°C) until the sensory experiment was performed, for which the trout were thawed and stored for 3, 5, 7 and 14 days in ice respectively. The sensory experiment included objective sensory profiling, of samples which were heat treated in a convention oven at 100°C until the core temperature was 70°C. The sensory panel consisted of 11 assessors which all were tested and trained. The sensory analysis included descriptors related to the odour, appearance, flavour and texture. After 3 days of storage in ice an impact of lipid source is seen. Inclusion of linseed oil resulted in a sensory profile comparable to the use of fish oil in the feed. While some of the other vegetable oils, especially grape seed oil results in a sensory profile rather different from the trout that had fish oil. However, this difference observed after 3 days of storage did not appear after a longer storage time, and consequently no differences in the sensory characteristics is observed after the 5 days of storage in ice. Nevertheless after 7 days in ice some differences are appearing again. Here the trout which have had rapeseed and grape seed oil in the feed has a more neutral flavour and odour compared to the other ones. After 14 days of storage the protein source had an effect, and the trout which received fishmeal in the feed were more tainted. Therefore, it is seen that the shelf-life is increased by feeding the fish with vegetable protein compared to fish meal. The conclusion of the experiment therefore was that both dietary vegetable protein and lipid sources c

The aim of this work was to study whether the type of protein and lipid source in feed for organic Rainbow trout (Onchorhynchus mykiss) influenced the sensory quality. The protein sources were fishmeal and a matrix of organic vegetable plant mealsproteins, while the lipid sources were fish oil and organic oils of linseed, sunflower, rapeseed and grape seed, respectively. Sensory profiling was performed after 3, 5, 7 and 14 days of storage in ice. Besides sensory analysis also lipid profiles weare measured. The resultsed showed that the lipid type in the feed aeffected the sensory characteristics after 3 days of storage. Especially the trout that had grape seed oil in the feed had a different sensory profile than the trout that had fish oil in the feed. These differences could be explained by the lipid profiles in the fillets. Also after 7 days of ice storage differences in the sensory profile wereas observed again as a result of the used lipid types used. After 7 days of ice storage ThusHere the trout that had grape seed oil orand rapeseed oil for instance had a more neutral flavor and odor profile compared to the other trout fed on linseed or sunflower oil´s. After 14 days of storage no effect of lipid type in the feed was observed, but the trout which had fish meal as protein source had higher intensity of several negative sensory descriptors compared to trout that had the vegetable protein matrix. Overall the results showed that the dietaryfeeds content of protein and lipid aeffecteds the sensory characteristics of the trout in different ways during the ice storage period.

The aquatic ecosystem represents a large number of organisms adapted to living conditions remarkably different from the land-living ones. For instance fish generally possess an eminent bioactive defense to protect them from the high bacterial load in water, and must be expected to harbor a large number of bio-components such as bioactive peptides for this purpose. Tissue and proteins from e.g. fish gills, skin and viscera could be a new source of peptides that could have a nutritional and pharmaceutical value, and be used in health and functional foods and thereby increasing the value adding of secondary marine products. Only few naturally occurring bioactive peptides have been characterized such as the antimicrobial polypeptide piscidines from gills. It is therefore hypothesized, that fish tissue also contains numerous other peptides with other bioactive properties. The approach in this project is therefore to extract and identify naturally occurring bioactive peptides from different tissues from salmon. A number of aqueous extracts were made from gills, skin and belly flap. In order to preserve the bioactivity of the peptides mild extraction procedures as acidic, basic and aqueous solutions were used. Combination of different extraction conditions such as with/without boiling, with/without inhibitor and variation of pH resulted in a total of 36 extracts. The activity of the extracts was analyzed in vitro for ACE (angiotensin-converting enzyme) inhibiting activity, and anti-oxidative activity (Free Radical Scavenging assay). A number of extracts showed high ACE inhibiting and anti-oxidative activity. The extracts were then size fractionated by ultrafiltration using a 10 kDa filter, and relevant fractions below 10 kDa from gills, skin and belly flap were further fractionated by gel-filtration on a Superdex peptide HR 10/30 column. Peptide fractions were collected and freeze-dried and will be further characterized with LCMS and MS/MS.

Feed production for aquaculture of carnivore fish species relies heavily on protein and lipid from the limited resources of wild fish and other sea living organisms. Thus the development of alternative feeds replacing fish meal and oil with components of vegetable origin is important for a sustainable production of fish from aquaculture. However, such a change in feed will have an effect on the fish composition and metabolism and may also affect eating quality as well as different health and nutritional properties. A proteomic approach was taken to compare the muscle protein profile of rainbow trout fed two different diets identical in protein and oil content, but with diet C based on fish meal and oil and diet V based on rapeseed oil and vegetable proteins. In addition to the proteomic investigation the textural properties of the fish were analysed by sensory profiling. Protein expression profiles were achieved by 2- dimensional gel electrophoresis. The result showed that 40 spots were significantly (p

The aim of this work was to study whether the type of protein and lipid source in feed for organic Rainbow trout (Onchorhynchus mykiss) influenced the sensory quality. The protein sources were fishmeal and a matrix of organic vegetable plant mealsproteins, while the lipid sources were fish oil and organic oils of linseed, sunflower, rapeseed and grape seed, respectively. Sensory profiling was performed after 3, 5, 7 and 14 days of storage in ice. Besides sensory analysis also lipid profiles weare measured. The resultsed showed that the lipid type in the feed aeffected the sensory characteristics after 3 days of storage. Especially the trout that had grape seed oil in the feed had a different sensory profile than the trout that had fish oil in the feed. These differences could be explained by the lipid profiles in the fillets. Also after 7 days of ice storage differences in the sensory profile wereas observed again as a result of the used lipid types used. After 7 days of ice storage ThusHere the trout that had grape seed oil orand rapeseed oil for instance had a more neutral flavor and odor profile compared to the other trout fed on linseed or sunflower oil´s. After 14 days of storage no effect of lipid type in the feed was observed, but the trout which had fish meal as protein source had higher intensity of several negative sensory descriptors compared to trout that had the vegetable protein matrix. Overall the results showed that the dietaryfeeds content of protein and lipid aeffecteds the sensory characteristics of the trout in different ways during the ice storage period.

A new and simple method to distinguish between cathepsin B and cathepsin L in crude extracts of herring (Clupea harengus) muscle has been established. An acid treatment of crude extracts (exposed to pH 3 for 5 min) activated a latent form of cathepsin L and inactivated cathepsin B. Furthermore, in neutral crude extract, the hydrolysis of benzyloxycarbonyl-L-phenylalanyl-L-arginyl-4-methylcoumarine (Z-Phe-Arg-MCA) (cathepsin B and cathepsin L substrates) was between 0% and 15% of the hydrolysis of benzyloxycarbonyl-L-arginyl-L-arginyl-7-amino-4-methylcoumarine (Z-Arg-Arg-MCA; cathepsin B substrate). Cathepsin B activity is measured in neutral extract using the specific cathepsin B substrate Z-Arg-Arg-MCA and cathepsin L activity is measured in acid-treated extract with Z-Phe-Arg-MCA as substrate. The specific cathepsin B inhibitor, CA-074, did not inhibit the Z-Arg-Arg-MCA significantly without affecting the Z-Phe-Arg-MCA activity. An acid treatment of the crude extract is therefore a more advantageous approach to discriminate between cathepsin B and cathepsin L activities.

Udgivelsesdato: September

Måling med nærinfrarødt (NIR) lys er et godt supplement til de nuværende metoder til at følge modningen af sild saltede i tønder. Det viser resultaterne af et forskningsprojekt udført i samarbejde mellem Lykkeberg A/S, Danmarks Fiskeriundersøgelser og Den Kgl Veterinær- og Landbohøjskole. Ved hjælp af avanceret matematik er det nemt og hurtigt at bestemme modningsgraden af sild direkte fra en NIR måling.

Near-infrared reflectance (NIR) spectroscopy in the spectral range of 1000-2500 nm, was measured directly on brine from barrel salted herring, to investigate the potential of NIR as a fast method to determine the protein content. A principal component analysis performed on the NIR spectra shows two groups, separating the first 100 days of storage from the storage time exceeding 100 days. A partial least-squares regression model between selected regions of the NIR spectra and the protein content yields a correlation coefficient of 0.93 and a prediction error (RMSECV) of 0.25 g/100 g. The results clearly indicate that NIR spectroscopy has a potential as a fast and noninvasive method for assessing the protein content in brine from barrel salted herring, which again may be used as an indicator for the ripening quality of barrel salted herring.

The sensory properties of marinated herring produced immediately post mortem of raw material from different fishing ground and seasons were described and related to biological, biochemical and functional properties. Subtle variation was encountered in the appearance of whole marinated herring fillets. Fishing ground did not influence the odor, flavor or texture, but there was an apparent effect of season on the sensory profile. The sensory properties were influenced by body weight, but not by age, sex and gonad maturity. The influence of varying lipid content, water content and liquid holding capacity resulted in similar effects showing the high correlation between these properties. The results indicated that variation in sensory quality observed by the industry is not primarily due to the parameters fishing ground and season