Effekt av pankreas sykdom og ulike saltebetingelser på kvaliteten til rå og kaldrøkt Atlantisk laks (Salmo salar L.)

Fillet quality of farmed Atlantic salmon (Salmo salar L.) is affected by a broad range of preand post-mortem factors. This thesis focuses mainly on the impact of pancreas disease (PD), salt composition and salting method on pigment concentration and colour of raw and coldsmoked salmon fillets, but fillet composition, texture and drip losses are as well considered. The fish material used to study effects of PD on fillet quality was sampled from commercial farming locations to obtain a broad overview and identify potential common properties of PD affected salmon (Paper I). The farming locations participated in a cohort study reported by Jansen et al. (2010), hence the salmon were sampled from populations with a well documented disease history. Salmon from seven farms were diagnosed with PD (diagnosed 0-12 months prior to slaughtering); salmon from one farm were infected with salmonid alpha virus (SAV) without an outbreak of PD, whereas salmon from two farms had no records of PD diagnosis and worked as control farms. To obtain knowledge on underlying causes to quality deviations of PD affected salmon, individuals with different PD pathology within a population diagnosed with PD at time of slaughtering was investigated (Paper II). Anecdotal information indicates that PD may cause poor general muscle quality and in particular pale and irregular colouration. Salmon diagnosed with PD at slaughter, or six months prior to slaughter confirmed this. Changes in quality in the order of their appearance were decreased CF, depleted muscle glycogen, increased drip loss of raw muscle, paler colour, depleted protein and finally harder texture in smoked salmon fillets. Salmon infected with salmonid alphavirus (SAV) without a PD outbreak and salmon diagnosed one year before slaughtering, had similar quality as unaffected fish, although paler colour might occur even after one year recovery. Within a population of farmed Atlantic salmon diagnosed with PD at time of slaughtering, a large variation was observed among individuals in pathological profile, gene expression profile in heart tissue, and fillet quality characteristics. Deteriorated quality and dysfunction of the digestive system was most pronounced in fish with severe loss of pancreas. Dry salting significantly reduced the stability of carotenoids in the fillet surface of coldsmoked salmon fillets as compared to injection salting (Paper IV). The salt content in pre rigor injection salted fillets was similar as those salted post rigor (2.4% versus 2.6%, respectively), whereas the fillet colour was more translucence. However, injection salting of pre rigor fillets can be recommended. Moreover, state of rigor mortis at time of salting had no effect on the carotenoid stability. Low correlations between colorimetric parameters and content of carotenoids in the fillet surface, illustrated that additional factors affects the visual appearance of cold smoked salmon. Nitrite salt curing (Paper III) improved the colour of cold-smoked salmon fillets (more reddish, darker and less yellowish). However, only slight higher carotenoid stability during processing was observed. The improved colour was most probably related to formation of nitrosomyoglobin. Salmon fillets treated with nitrite (fine refined salt added 0.6% sodium nitrite) had a relatively high amount of residual nitrite, however higher contents of Nnitrosoamines were not observed. It is concluded that salmon diagnosed with PD at slaughter, or six months prior to slaughter showed deteriorated fillet quality, whereas salmon infected with salmonid alphavirus (SAV) without a PD outbreak and salmon diagnosed one year before slaughtering, had similar quality as unaffected fish. Moreover it is concluded that nitrite salt improved the appearance of cold-smoked salmon fillets and dry salting reduced the stability of carotenoids in the fillet surface as compared to injection salting.Filetkvalitet hos oppdrettslaks (Atlantisk laks, Salmo salar L.) blir påvirket av ulike faktorer pre og post mortem. I denne avhandlingen er hovedfokuset rettet mot betydningen av pankreas sykdom (PD), saltets sammensetning og saltemetode i forhold til pigmentkonsentrasjon og farge hos rå og kaldrøkte laksefileter. I tillegg er filetsammensetning, tekstur og væsketap tatt i betraktning. For å studere effekten av PD på filetkvalitet hos laks, ble det hentet fisk fra kommersielle oppdrettsanlegg. Dette ble gjort for å få en bred oversikt og for å identifisere potensielle fellestrekk hos PD affisert laks (Artikkel I). Oppdrettsanleggene som ble benyttet var også med i en kohortstudie beskrevet i Jansen et al. (2010), noe som ga fisken en veldokumentert sykdomshistorie. Laks fra syv anlegg var diagnostisert med PD (diagnostisert 0-12 måneder for slakting) og ett anlegg var infisert med SAV uten at PD utbrudd var registrert. Laks fra to andre anlegg var uten tegn til PD og fungerte som kontrollanlegg. For å finne underliggende årsaker til kvalitetsavvik hos PD diagnostisert fisk, ble individer fra samme populasjon (diagnostisert med PD under slakting), men med ulik PD patologi undersøkt (Artikkel II). Anekdotisk informasjon indikerer at PD kan forårsake generelt dårlig muskelkvalitet, og da spesielt lys og ujevn farge. Laks diagnostisert med PD under slakting, eller seks måneder for slakting bekrefter dette. Endringene i kvalitet i forhold til når de inntreffer var; redusert kondisjonsfaktor, forbruk av glykogen, økt væsketap i rå muskel, blassere farge, forbruk av protein og til slutt hardere tekstur i kaldrøkte fileter. Laks infisert med SAV uten utbrudd av PD og laks diagnostisert ett år for slakting, hadde lik kvalitet som upåvirket fisk, selv om laks med blassere farge kan eksistere selv ett år etter sykdom. I en populasjon av Atlantisk laks diagnostisert med PD under slakting, ble det observert stor variasjon mellom ulike individer. Variasjonen viste seg i patologisk profil, genekspresjonsprofil i hjertemuskel og i filetegenskaper. Forringet kvalitet og nedsatt fordøyelsessystem var mest synlig i fisk med kraftig redusert pankreas. Sammenlignet med injeksjonssalting reduserer tørrsalting stabiliteten til karotenoider i filetoverflaten hos kaldrøkt Atlantisk laks (Artikkel IV). Saltkonsentrasjonen i fileter injisert med salt pre rigor var forholdsvis lik de respektive filetene saltet post rigor (2,4 versus 2,6 %). Pre rigor injiserte fileter var samtidig lysere. Likevel kan injeksjonssalting av pre rigor laksefileter anbefales. Rigorstatus ved saltetidspunktet hadde ingen effekt på stabiliteten til karotenoidene. En lav korrelasjon mellom fargeparametre og innhold av karotenoider i kaldrøkt laks, viser at andre faktorer også påvirker det visuelle uttrykket av fileten. Nitrittsalting (Artikkel III) forbedrer fargen hos kaldrøkte laksefileter (filetene blir rødere, mørkere og mindre gule), selv om stabiliteten til karotenoidene kun øker marginalt. Forbedret filetfarge skyldes høyst sannsynlig dannelse av nitrosomyoglobin. Laksefileter behandlet med nitritt (fint raffinert salt tilsatt 0,6 % natrium nitritt) hadde et relativt høyt innhold av resterende nitritt, uten at det ble funnet høyere verdier av N-nitrosoaminer. Det er konkludert med at laks diagnostisert med PD under slakting, eller 6 måneder for slakting, viser redusert filetkvalitet. Laks infisert med SAV uten utbrudd av PD og laks diagnostisert med PD ett ar for utbrudd, viser lik kvalitet som upåvirket fisk. Videre er det konkludert med at nitrittsalt gir bedre farge hos kaldrøkte laksefileter og tørrsalting reduserer stabiliteten til karotenoider sammenlignet med injeksjonssalting.Norwegian Fishery and Aquaculture Industry Research Found, FHF ; Norwegian Seafood Association, NS

The potential of anthocyanin-loaded alginate hydrogel beads for intelligent packaging applications: Stability and sensitivity to volatile amines

pH indicators have emerged as promising tools for real-time monitoring of product freshness and quality in intelligent food packaging applications. However, ensuring the stability of these indicators is critical for practical use. This study aims to evaluate the stability of anthocyanins-loaded alginate hydrogel beads of varying sizes at different temperatures under accelerated light conditions and relative humidity (RH) levels of 53% and 97% during 21 days of storage. Moreover, their sensitivity to the principal spoilage volatiles of muscle food products such as ammonia (NH3), dimethylamine (DMA) and trimethylamine (TMA) was investigated. The half-life of cyanidin-3-glucoside in small hydrogel beads was roughly twice as long as that of the larger beads under accelerated light exposure at 4 °C and they were less likely to undergo noticeable color changes over time. Both sizes of hydrogel beads stored at 97% RH and 4 °C showed color stability over the 21-day period with minimal color variation (|ΔE| ≤ 3). The UV–vis spectra of the purple corn extract exhibited changes across pH 2 to 12, as evidenced by the visible color variations, ranging from pink to green. The limit of detection (LOD) for NH3 was 25 ppm for small beads and 15 ppm for large ones. Both types of beads exhibited similar LOD for DMA and TMA, around 48 ppm. This research showed that alginate hydrogel beads containing anthocyanins from purple corn are a viable option for developing intelligent packaging of muscle foods. Furthermore, the use of hydrogel beads of different sizes can be customized to specific muscle foods based on the primary spoilage compound generated during spoilage

Physiological and flesh quality consequences of pre-mortem crowding stress in Atlantic mackerel (Scomber scombrus)

In commercial wild capture pelagic fisheries it is common practice to crowd catches to high densities to allow efficient pumping onboard. Crowding during the final stages of purse seine capture for small pelagic species often results in intense and sustained behavioural escape responses. Such a response may trigger a shift in energy production from aerobic to anaerobic pathways and result in metabolic acid accumulation and exhaustion of intracellular reserves of ATP. Where there is insufficient time or opportunity to recover to physiological equilibrium before death, pre-mortem stress may be an important determinant of fillet quality, as has been shown for a variety of farmed fish species. However, there is currently a lack of knowledge related to the flesh quality implications of capture stress for wild captured species in European waters. Here we show that crowding results in a physiological stress response that has consequences for flesh quality in the wild captured species Atlantic mackerel (Scomber scombrus). Using small schools in tanks and aquaculture net pens in three separate experiments, we found crowding results in physiological changes in mackerel consistent with an acute stress response and anaerobic metabolism. Consequently, we found crowded fish had more acidic pre- and post-mortem muscle pH as well as indications of faster onset and strength of rigor mortis and increased cathepsin B & L activity. We examined fillet flesh quality after two and seven days of ice storage and found reduced green colouration, increased gaping (separation of muscle myotomes) and reduced textural firmness associated with fish which had been crowded. However, the effects on quality were dependant on experiment and/or storage time. These results indicate the potential of crowding capture stress to influence the flesh quality of an economically important species and may have important implications for the wild capture pelagic fishing industry.publishedVersio

The quality of frozen–thawed Atlantic salmon (Salmo salar L.) fillets as affected by sub-chilling before freezing

Background To maintain the quality of frozen Atlantic salmon after thawing and highlight the potential for moving from air fright to boat for long-distance export, a study was designed to investigate the effects of sub-chilling before rapid freezing on the quality of thawed fillets. Atlantic salmon chilled on wet ice before filleting and freezing was used as a control for the experimental factor chilling, whereas fresh fillets were used for the frozen–thawed samples. Results The pre-freezing chilling method interacted with the storage protocol and significantly affected the product. For fresh stored fillets, sub-chilling improved the microbiological and textural stability and degradation of proteins. After 1 month of frozen storage, sub-chilled fillets gave better color and textural properties, less adenosine triphosphate degradation and protein denaturation. In addition, sub-chilled 4-month-frozen fillets also showed improved microbial stability compared to those initially chilled with ice before frozen storage. Quality was lost as a function of storage. Fresh fillets generally had higher bacterial counts, surface breaking force, firmness, hue and contents of inosine monophosphate, and lower drip loss and inosine (HxR) levels than those stored frozen–thawed. Moreover, 4-month-frozen fillets had higher HxR levels and lower psychrotrophic viable count growth than those that were frozen for 1 month. The time fillets were stored frozen did not profoundly affect their quality. Conclusion It is concluded that a frozen product might be competitive with a fresh product when sub-chilling is performed before freezing, especially when including the environmental benefits of frozen export by boat rather than air freight. © 2024 The Author(s). Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.publishedVersio

Redusere avrenning fra ferskfisk transport på lastebiler

By law, fresh fish is transported on ice in the EEA. This system is tried and proven and works perfectly except that upward of 1000 L of meltwater drain onto the road from a typical trailer load. This is most noticeable near packing and slaughterhouses, on ferries, and on certain roads (e.g. Laksevegen Fv. 714 in Trøndelag). This is a nuisance, publicity issue, and a matter of road safety.Redusere avrenning fra ferskfisk transport på lastebilersubmittedVersio

Mild processing of seafood—A review

Recent years have shown a tremendous increase in consumer demands for healthy, natural, high-quality convenience foods, especially within the fish and seafood sector. Traditional processing technologies such as drying or extensive heating can cause deterioration of nutrients and sensory quality uncompilable with these demands. This has led to development of many novel processing technologies, which include several mild technologies. The present review highlights the potential of mild thermal, and nonthermal physical, and chemical technologies, either used alone or in combination, to obtain safe seafood products with good shelf life and preference among consumers. Moreover, applications and limitations are discussed to provide a clear view of the potential for future development and applications. Some of the reviewed technologies, or combinations thereof, have shown great potential for non-seafood products, yet data are missing for fish and seafood in general. The present paper visualizes these knowledge gaps and the potential for new technology developments in the seafood sector. Among identified gaps, the combination of mild heating (e.g., sous vide or microwave) with more novel technologies such as pulsed electric field, pulsed light, soluble gas stabilization, cold plasma, or Ohmic heat must be highlighted. However, before industrial applications are available, more research is needed.publishedVersio

Selective precipitation reaction: a novel diagnostic test for tissue pathology in Atlantic Salmon, Salmo salar, infected with Salmonid Alpha-Virus (SAV3)

While investigating biomarkers for infection with salmonid alphavirus (SAV), the cause of pancreas disease (PD), a selective precipitation reaction (SPR) has been discovered in serum which could be an on-farm qualitative test and an in-laboratory quantitative assay for health assessments in aquaculture. Mixing serum from Atlantic salmon, Salmo salar, with SAV infection with a sodium acetate buffer caused a visible precipitation which does not occur with serum from healthy salmon. Proteomic examination of the precipitate has revealed that the components are a mix of muscle proteins, for example enolase and aldolase, along with serum protein such as serotransferrin and complement C9. The assay has been optimized for molarity, pH, temperature and wavelength so that the precipitation can be measured as the change in optical density at 340 nm (Δ340). Application of the SPR assay to serum samples from a cohabitation trial of SAV infection in salmon showed that the Δ340 in infected fish rose from undetectable to a maximum at 6 weeks post-infection correlating with histopathological score of pancreas, heart and muscle damage. This test may have a valuable role to play in the diagnostic evaluation of stock health in salmon

Impact of soluble gas stabilisation (SGS) technology on the quality of superchilled vacuum-packed salmon portions following different cold chain scenarios

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Reduksjon av smeltevann fra fisketransport

Undersøkelser i prosjektet viser at det er store forskjeller mellom de ulike aktørene i bransjen med tanke på temperaturkontroll av fisk. Hovedutfordringen med avrenning ligger nok hos produsentene, der fisken generelt ikke blir tilfredsstillende nedkjølt. De aller fleste som deltok i studien har et temperaturmål på 1-3 °C for fisk som pakkes med is, noe som vil gi smelting av is og avrenning under lagring og transport. Det finnes flere tilgjengelige metoder for å samle opp smeltevann som produseres. Tette kasser fremstår som et alternativ som raskt kan implementeres hvis fisken er tilstrekkelig nedkjølt. Et annet alternativ er å montere oppsamlingstanker på lastebilene. Det var til dels store forskjeller hvilket fokus avrenning hadde i Irland, Island og Færøyene. Færøyene hadde det beste systemet med organisert oppsamling og mottak av avrenningsvann. Den matematiske modellen som ble utviklet, bekrefter at temperaturen på fisken har størst innvirkning på avrenningen, men at lastebilen også må gjøre sin del av jobben. Det anbefales at fisken er kaldere enn 1 °C, og at lastebilen stilles inn på -1 til 0 °C.Reduksjon av smeltevann fra fisketransportpublishedVersio

Norwegian Consumers’ Skepticism towards Smoke-Flavoring of Salmon—Is It for Real?

The aim of the present study was to explore Norwegian consumers’ attitudes toward smoke-flavoring of cold smoked salmon (CSS), by conducting a digital survey and focus group discussions. Some of the smoke-flavoring techniques, like atomized purified condensed smoke, is considered healthier than conventional smoking. Manufacturers of CSS are, however, hesitant to use all kinds of smoke-flavoring due to expected consumer skepticism. In the digital survey, the expected skepticism was confirmed (n = 487). Only 15% of the respondents were positively oriented toward smoke-flavoring of CSS. The selection criterion for the focus group discussion was based on the results from the survey and resulted in three attitude-oriented focus groups (negative, neutral, and positive). The negative focus group considered smoke-flavored CSS to be unnatural and out of the question to buy or eat. Unlike the negative focus group, the neutral group was curious to learn more and open to potential smoke-flavor benefits. However, credible information or science was crucial to influence CSS choice. Future studies may investigate whether the existent of this large group of curious neutral consumers (47% of the respondents) influence manufacturers (of CSS) skepticism or how various types of product information could steer consumer acceptance of smoke-flavoring of CSS.publishedVersio