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Lipids from residual fish raw materials: Quality assessment by advanced analytical methods
Full text linkPhD i bioteknologiPhD in Biotechnolog
Lipids from residual fish raw materials : Quality assessment by advanced analytical methods
No full textADDENDUM Figure 4, page 14; Copyright © 1996 From Food Chemistry by Nawar, W.W. (Fennema, O.R.ed). Reproduced by permission of Routledge/Taylor & Francis Group, LLC Paper I, VII and VIII are reprinted with kind permission from Elsevier, sciencedirect.co
Valorization of whitefish residuals generated onboard deep-sea vessels – from waste to value
Full text linkThe global population is projected to grow by 2 billion by 2050, increasing pressure on food and feed resources. In Norway, the whitefish sector and the deep-sea fleet represent a significant opportunity to enhance the utilization of residual raw materials. In 2022, 70 % of the residuals generated onboard deep-sea vessels were discarded at sea. These raw materials are rich in valuable nutrients, including health-promoting omega-3 fatty acids and proteins, which can be used in food or feed applications.
One of the key challenges in utilizing these raw materials is the rapid degradation of viscera and liver, which are highly susceptible to enzymatic and microbial breakdown, as well as lipid oxidation. This highlights the importance of developing optimal strategies for handling, storing, preserving and processing these raw materials onboard. Thermal treatment can be used to produce oil from the whole viscera or from out-sorted livers onboard. However, little is known about how sorting and raw material freshness affect the composition and quality of the oil. Silaging can be used to preserve either the whole viscera or viscera without livers, if livers are sorted out for separate oil production. The technology is cost-effective, and the low pH inhibits the growth of spoilage bacteria while creating favorable conditions for proteolytic enzymes to break down proteins, resulting in a liquid product that can be separated into oil and protein hydrolysate for feed applications. However, silage is often regarded as a low-value product with poor quality, highlighting the need for quality optimization.
This study investigates the impact of raw material freshness and sorting on the quality of oil produced by thermal treatment. The findings show that high-quality oil, rich in omega-3 fatty acids, can be produced from both viscera with liver and out-sorted livers. Processing shortly after catch led to a generally higher oil quality, but both viscera and liver could be stored for up to 2 days at 4 °C and still meet quality guidelines for human consumption. It was also demonstrated that significantly higher oil yields could be obtained if the raw materials were stored for 1 day or more. However, after 2 days of storage, an undesired emulsion layer formed during processing of the whole viscera.
Additionally, the research examines how raw material sorting, freshness, and the use of antioxidants affect the yield, composition and quality of the oil and protein hydrolysates obtained from silaging. The study demonstrates that preserving the raw material shortly after catch and using antioxidants significantly reduce the formation of lipid oxidation products, thereby improving oil quality. The findings also show that viscera can be stored for 1 day before silaging without compromising protein quality, though immediate processing yields hydrolysates with a higher protein content. Out-sorting the liver reduces the risk of emulsion formation but was not required to produce protein-rich hydrolysates.
Overall, this work demonstrates that the viscera and liver of whitefish can be valorized into ingredients that can either directly, or indirectly, enter the food value chain. Valorizing these currently wasted residuals can significantly contribute to sustainability by improving resource efficiency, enhancing human nutrition and reducing pressure on fishery stocks
“It’s not uncomplicated to say you simply cannot do it like this anymore” – a study of the Norwegian whitefish industry and the potential for improved utilization of rest raw materials
Full text linkThe Norwegian whitefish industry has long traditions and constitutes an important part of both economy and food production. Whitefish is a collective term for several lean fish species, the most important being cod (Gadus morhua) and saithe (Pollachius virens). Processing of whitefish generates substantial amount of rest raw materials (RRM) that are mainly used for animal feed, biofuels or wasted. However, in order to meet the growing demand for nutrition, while simultaneously protecting our environment, we need to change the way we produce food. Whitefish RRM is a source of several nutritional components, including high-quality proteins, that can be used for human consumption as part of a sustainable food production.
The aim of this thesis was to present a systemic and innovative approach to the Norwegian whitefish industry and the objective of improving the utilization of whitefish RRM generated during catch, landing, and processing. This approach involved the use of two paths of obtaining knowledge, and the combinations of those, to get a thorough understanding of the current potential for improved utilization of whitefish RRM. The first path involved the use of laboratory experiments to evaluate the effect of spawning on saithe RRM, the potential for upscaling biotechnological processing for bulk production of protein products and the refinement of these to increase bioactive properties. The second path involved a case study within the Norwegian whitefish industry to investigate how experiences, attitudes and practices among fishers, and the circumstances affecting these, could enable or complicate efforts to improve utilization of RRM. The knowledge obtained from the laboratory experiments and the case study were then combined in an overall evaluation.
Saithe RRM mainly consist of heads, backbones, and viscera. Spawning did not affect the nutritional composition of heads and backbones. These RRMs are also relatively stable compared to viscera and were selected for further processing. Processing of saithe RRM involved mincing, enzymatic hydrolysis and membrane ultrafiltration. Enzymatic hydrolysis in bioreactors enabled extraction of RRM protein content to a high-quality saithe protein hydrolysate (SPH). Regarding processing equipment, a need for powerful and energy-efficient solutions for mincing, agitation, and dewatering were identified. SPH was further processed by membrane ultrafiltration to concentrate small peptides, which are associated with several health beneficial bioactive properties including the ability to work as antioxidants. Spawning neither affected the quantity and quality, nor the antioxidative activity of SPH. Membrane ultrafiltration enabled a concentration of small peptides but did not increase antioxidative activity compared to SPH. Significant amount of the RRM protein content ends up in the secondary products of processing, which makes it important to find areas of applications for these as well.
Eight interviews with fishers of the whitefish industry resulted in the creation of three main themes. These concerned the term sustainability and its interpretation, the fragmented organization of the value chain, the development and implementation of regulations, and how this can affect rationalization, behaviour, and attitudes among fishers.
This thesis has identified logistical, technological, and sociocultural factors, in addition to factors concerning the raw material itself, that could affect the potential for improved utilization of whitefish RRM. While the availability and seasonal stability of saithe RRM could positively affect this potential, insufficient processing solutions, communication, management, and organization of the value chain could have a negative effect. This work does not provide a final solution, nor an all-encompassing truth, but can inspire other natural scientists to look beyond the limitation of traditional research methods and see the value in adopting and developing new methods for obtaining knowledge. Knowledge that could contribute to a sustainable development within the Norwegian whitefish industry, but also on a global level
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Lipid variation and stability in rest raw materials from Atlantic Cod (Gadus morhua): Insights into biochemical degradation during storage, and variation across individuals
Full text linkDenne oppgaven utforsker variasjon og stabilitet i lipider i restråstoff fra atlantisk torsk (Gadus morhua), med fokus på biokjemisk nedbrytning under lagring og variasjon mellom individer. Studien er en del av SUPREME-prosjektet, som har som mål å øke utnyttelsen og verdien av restråstoff i hvitfiskindustrien. Denne masteroppgaven inkluderer to studier, en variasjonsstudie og en stabilitetstudie. Variasjonsstudien vurderte lipidinnhold, lipidklasser og fettsyresammensetning (FA) sammen med fysiologiske egenskaper som vekt av slo og fiskelengde i sloprøver fra torsk, hvor lever og gonader er ekskludert. Fiskeprøvene i denne studien ble fisket fra tre forskjellige fiskestasjoner i Barentshavet. I stabilitetsstudie ble endringer i lipidegenskaper evaluert i lever og slo (inkludert lever) over en 6-dagers lagringsperiode ved kjøleforhold etterfulgt av en utvidet fryselagringsperiode. Resultatene viste minimal variasjon mellom individuelle sloprøver av torsk basert på lokasjon og kjønn, men signifikante forskjeller basert på mage- og tarminnhold, målt via slo-til-lengde-forholdet (VLR). Lipaseaktivitet var sannsynligvis ikke påviselig i stabilitetsstudien på grunn av forlenget lagringstid og gjentatte fryse-tine-sykluser. Frie fettsyrer (FFA) økte under lagring, noe som indikerer nedbrytning, mens triglyseridinnhold og lipidutbytte sank i både lever- og sloprøver. Disse endringene var mer uttalte i sloprøvene. Disse funnene bidrar til å forstå de biokjemiske prosessene i restråstoff fra torsk og øker kunnskapen for å utarbeide strategier for å forbedre bærekraftig utnyttelse i fiskeindustrien.This thesis explores lipid variation and stability in rest raw materials from Atlantic cod (Gadus morhua), focusing on biochemical degradation during storage and individual variation. The study is part of the SUPREME project, aiming to enhance the utilization and value of rest raw materials in the white fish industry. This master project includes two studies, the variation study and the stability study. The variation study assessed lipid content, lipid classes, and fatty acid (FA) composition, alongside physiological traits such as viscera weight and fish length, in viscera (excluding liver and gonads) from cod captured at three locations in the Barents Sea. Additionally, the stability study evaluated changes in lipid properties in the liver and viscera (including the liver) over a 6-day storage period at cooling conditions followed by an extended freezing storage period. Results revealed minimal variation between individuals based on locations and sex, but significant differences based on stomach and intestinal contents, measured via a viscera-to-length ratio (VLR). Lipase activity was likely undetectable in the stability study due to prolonged storage time and repeated freeze-thaw cycles. Free fatty acids (FFA) increased during storage, indicating degradation, while triglyceride content and lipid yield decreased in both liver and viscera samples, with the changes being more pronounced in the viscera samples. These findings contribute to understanding the biochemical processes in rest raw materials and support strategies to improve their sustainable utilization in the fishing industry
Oxidation of Fish Oil and Powder - Exploring Suitable Methods for the Determination of Oxidative Changes in Fish Oil and Powder
No full textLipidoksidasjon (harskning) er en av hovedårsakene til kvalitetsforringelse i mat, noe som begrenser muligheten for anrikning av marine n-3 fettsyrer i matvarer. De gunstige helseeffektene av langkjeda n-3 flerumettede fettsyrer er godt dokumentert, men mange mennesker dekker ikke sitt daglige behov av n-3 på grunn av den uønskede fiskesmaken og lukten forårsaket av lipidoksidasjon. Analysemetoder som kan måle oksidative endringer i komplekse matmatriser er høyst nødvendig, og interessen for raske metoder er stor. Det er imidlertid omfattende utfordringer og begrensninger knyttet til de tradisjonelle metodene.
Denne studien undersøkte egnede metoder for å bestemme oksidative endringer i fiskeolje og pulver ved å utføre et lagringseksperiment i opptil 4 uker ved 40 °C med oksygentilgang. Denne forskningen bidrar til å fylle et behov for informasjon angående en metode til å måle oksidative endringer i fiskepulver uten å ekstrahere ut oljen i pulveret, hovedmålet med denne oppgaven. GC-MS ble funnet til å være en egnet metode for å bestemme den oksidative statusen i fiskepulver direkte, uten et ekstraksjonstrinn som kan forverre den oksidative tilstanden.
Analysene i denne studien fant ingen holdepunkt for at pulveret var mer stabilt enn oljen, eller at pulveret beskyttet og stabiliserte oljen i pulveret. Pulveret virket i utgangspunktet mer oksidert sammenlignet med oljen, og oksiderte raskere enn oljen. Både pulveret og oljen ble lagret med oksygentilgang (for å fange de flyktige forbindelsene), noe som kan ha forverret den oksidative tilstanden under lagring i fryser sammenlignet med om prøvene hadde blitt flushet med nitrogen før lagring. Basert på resultatene i denne studien ga dynamisk headspace GC-MS-analyser nyttig informasjon i forskningen på oksidative endringer i fiskeolje og pulver. I prosessen ble GC-MS metodeparametere for analyse av flyktige komponenter i fiskeolje og pulver optimalisert.
Denne studien sammenlignet også de tradisjonelle metodene for å bestemme PV og AV med den raske metoden, CDR FoodLab, for å undersøke hvor egnet den raske metoden er mot de tradisjonelle metodene. Det ble funnet sterke korrelasjoner mellom metodene.
Peroksidverdi (PV) ble brukt som en parameter for primære oksidasjonsprodukt, og Anisidinverdi (AV), Tiobarbitursyrereaktive stoffer (TBARS), og Gasskromatografi-Massespektroskopi (GC-MS) ble brukt til å analysere sekundære oksidasjonsprodukter
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