Primary silicon crystals grown from an Al-Si melt has been investigated by solidifying directionally and under electromagnetic field. The goal of this thesis was to increase the size of the primary Si crystals and to agglomerate the crystals to one part of the melt. If achieved, this could simplify the following acid leaching process that is necessary to collect the crystals from the melt. Seven experiments were conducted in a resistance furnace with directional solidification to investigate the agglomeration and size of the Si crystals. A mono-crystalline Si seed was added to the Al-Si melt in three of these experiments as an attempt to increase the crystal growth. The impact of stirring in the melt before solidification was investigated. Al-Si melt was directionally solidified without the aid of seed in three experiments. The silicon content in the alloy and pulling rate during solidification was varied in these experiments to find the appropriate Si crystal growth conditions. The growth of silicon crystals from a mono-crystalline Si seed without aluminium was performed to investigate the impact aluminium had on the seeded growth. One experiment was conducted in an induction furnace to investigate the influence electromagnetic force has on the agglomeration of primary Si crystals. Agglomeration of Si primary crystals was found not to be successful for either directional solidification or electromagnetic force method, as the crystals were not gathered to one part of the melt. The size of the primary Si crystals was not as large as expected and addition of mono-crystalline Si seed did not improve the crystal size. A single Si crystal was successfully grown from a mono-crystalline Si seed when there was no aluminium in the melt.

Renewable energy production featuring silicon photovoltaic solar cells are of considerable interest to reduce pollution and related environmental changes. Improvements in efficiency along with reductions in cost are key elements to large scale implementation of this technology. Some suggested and attempted methods of improvements that deserves mentioning are: modifying the energy of incident light to better suit the existing band gap along with reduction in losses by applying surface texturing and nitride coatings. Looking to nature for inspiration reveals diatoms and their frustules having pore structures displaying excellent light harvesting abilities. Thus an implementation of such structural features with regards to solar cell improvements would be highly desirable. This thesis was aimed at performing modifications of diatom frustules surfaces by deposition of oxides known to possess properties of up and down-conversion of light as well as attempting to convert diatom frustules to silicon nitride replicas. Coating frustules with oxides possessing properties of up and down-conversion of light combines light harvesting properties of frustules with spectral modifications of incident light. This offers possibilities of solar cell improvements upon implementation. Nitriding of diatom frustules preserves structural features of the frustules and offers increased mechanical, chemical, thermal and anti-reflecting properties for possible solar cell use. Diatom frustules of the species Coscinodiscus wailesii and Coscinodiscus sp. were utilized in all experimental work during this thesis. An initial temperature exposure experiment was performed at temperatures ranging from 400oC-1200oC with increments of 200oC, to gage thermal response of the frustules. In another set of experiments diatom frustules were subjected to one, two and four dip coatings in one of two different precursor solutions. One solution consisted of erbium and yttrium chloride dissolved in a mixture of ethylene glycol and acetonitrile while the other solution consisted of manganese and zinc chloride dissolved in ethylene glycol and acetonitrile. Post dip coating, frustules were annealed at 800oC in normal atmosphere, decomposing chloride precursors to corresponding oxides. Nitriding of frustules was attempted by simultaneous metallothermic reduction in a purpose built reactor vessel where necessary nitrogen was supplied in the form of ammonia at 650oC and 800oC. Ammonia was generated by thermal decomposition of ammonium chloride mixed with calcium oxide. Post experiments, frustules were characterized by use of scanning electron microscope (SEM) featuring energy dispersive x-ray spectrometer (EDS), fluorescence microscopy, photoluminescence spectroscopy and Raman spectroscopy. Frustules in the temperature exposure experiment were found to display small changes to the pores at 600oC. At 800oC the changes were more severe and the changes were found to increase with increasing temperature until complete destruction of the pores along with visible external changes took place at 1200oC. For the coating experiments, no photoluminescent properties were found to exist for frustules coated once or twice. Frustules coated four times were found to display photoluminescent behavior for both types of coatings. Frustules subjected to four coatings with Zn/Mn solution were found to display more temperature related changes in the pores as compared to frustules coated four times with Y/Er solution. Frustules coated with Zn/Mn solution, were found to be contaminated by elevated levels of tin, possibly influencing both thermal and photoluminescent properties. Frustules subjected to simultaneous metallothermic reduction and nitriding at 650oC were found to suffer low conversion and thus only superficial nitride formation. Frustules nitrided at 800oC were found to display higher conversion to silicon nitride. The formed nitride was determined to be β-silicon nitride by Raman spectroscopy. The frustules were also found to contain elevated levels of reduced silicon, for the frustules nitrided at 800oC, this silicon was found to be a mixture of amorphous and nanocrystalline. The nanocrystalline silicon was found to have a crystalline size of ~2.2 nm.

En transdermal leveringsform gir store fordeler framfor oral, intramuskulær og intravenøs levering, men byr også på noen utfordringer. Den største utfordringen er at kun et begrenset antall molekyler kan administreres på denne måten. Hudens øverste lag, stratum corneum, er en effektiv barriere, som bare noen molekyler kan penetrere. Disse molekylene er karakterisert som lavmolekylære (≤ 500Da) og lipofile (hydrofobe). Det er gjennomført forsøk på fullskala hud fra mennesker, for å undersøke om vannløselige (hydrofile) molekyler som fiskegelatinpeptider og G-blokk vil kunne penetrere huden og diffundere ned i dermis. G-blokk og fiskegelatin ble først fraksjonert for å lage mest mulig monodisperse prøver, og deretter fluorescensmerket med alexa 488/532 fluorokrom. De fluorescensmerkede prøvene ble løst i 60 % dimetyl sulfoksid (DMSO), før de ble påført epidermis-siden av hudbiter montert i Franz-celler. Huden ble først forbehandlet med mikronåler. Konfokal laser skanning mikroskop ble benyttet for å undersøke fluorescensintensiteten i vevet, og dermed penetrasjonsevnen til de ulike G-blokkene og fiskegelatinpeptidene. Ved hjelp av hyperspektral avbildning ble det også undersøkt fluorescensintensitet i tillagde hudfantomer. I oppgaven er det lagt vekt på hvordan penetrasjonsevnen til ulike molekyler avhenger av molekylvekt, merkningsgrad, forbehandling (mikronåler og DMSO) og individuelle forskjeller mellom donorer. Det ble også undersøkt hvor lang tid det tar før det observeres en betydelig mengde fiskegelatinpeptider i vevet.Noen G-blokker og fiskegelatinpeptider ble funnet til å kunne penetrere huden. Det ble påvist at en forbehandling med mikronåler og 60 % DMSO som vehikkel, øker permeabiliteten til huden. I tillegg ble det observert store variasjoner i penetrasjonsevnen til prøvene når forsøk ble utført på samme eller ulike donorer. Fiskegelatinpeptider ble vist til å begynne å penetrere forbehandlet hud allerede etter 8 timer, men først etter 18 timer inkubasjonstid ble det observert en betydelig mengde fiskegelatinpeptider i vevet. Det ble funnet en sammenheng mellom fraksjon høymolekylære peptider i fiskegelatinprøvene og fluorescensintensitet i vevet etter endt inkubasjonstid (24 timer). Det ble observert høyere fluorescensintensitet i vevet etter påførte prøver med høyt innhold av lavmolekylære peptider, enn for prøver med flere høymolekylære peptider. Det ble også observert en sammenheng mellom merkningsgrad og detektert penetrasjonsevne. Der prøver med høy merkningsgrad ga høyere fluorescensintensitet i vevet og fluorescens i reseptorfasen, enn prøver med lavere merkningsgrad. I tillegg ble det observert lite eller ingen elektrostatisk binding av fluorescensmerkede prøver av fiskegelatin og G-blokk til pappilær dermis, mens stratum corneum ble observert som den store barrieren i huden ved at den hadde høyest fluorescensintensitet. Fiskegelatinprøvene ble funnet veldig polydisperse selv etter fraksjonering ved hjelp av dialysemembraner med ulik størrelse. Det er observert liten sammenheng mellom molekylvekts cut-off på dialysemembran, og faktisk størrelse av peptider som trekker ut.Hyperspektral avbildning ble funnet til å fungere for hudfantomer med mer enn 25 mg kovalent merket gelatin.

Alginate scaffolds show good promise for bone tissue engineering using stem cells. This is due to the fact that alginate is biocompatible, non-immunogenic, and in addition may direct differentiation of stem cells into a given phenotype. Finally, due to their ability to gel at physiological conditions, living and functional tissue are easily encapsulated into alginate beads. Alginate beads can be modified in a range of ways, not only to enhance the matrix stiffness and stability, but also to promote cell adhesion and direct differentiation towards a given phenotype. A method currently used to encourage bone growth is to mineralize the alginate beads, thus mimicking the structure of bone in vivo. Recently, Xie et al. (2011) demonstrated that enzymatic mineralization of alginate beads serves as a potent method for mineralizing beads as lower concentrations of CaCl2 is needed, which is beneficial for cell viability. In addition, the enzymatic method produces alginate beads with a uniformly distribution of calcium phosphate (CP) and stiffer mechanical properties. Mesenchymal Stem cells (MSCs) have the potential to differentiate into a variety of tissues, including cartilage, adipose, muscle and bone. MSCs extracted from bone marrow seem to possess the greatest potential for bone tissue engineering, as they are more easily differentiated into osteogenic phenotypes when compared with MSCs from e.g. adipose tissue. The main objective in the present study was to encapsulate MSCs into alginate beads mineralized with alkaline phosphatase (ALP) and study cell survival, as well as their potential to differentiate into mature osteoblasts inside the beads. To mineralize beads (ALP) was added to the alginate solution, whilst the precursors were added to the growth medium. The mineralization medium was changed every 3 hours (12 hours over night) for the first 2 days post encapsulation.Cell viability was surveyed by live/dead assay and imaging by Confocal Laser Scanning Microscopy (CLSM), and metabolic activity by Alamar Blue (AB) and colorimetric techniques. Examination of cell morphology was accomplished by phalloidin/DRAQ5 staining. Moreover, to investigate cell differentiation, PCR analysis on selected RNA candidates was performed. Quantification of mineral content was accomplished by running Alizarin Red-S (ARS-S) assay. ALP activity was determined using ALP assay. Finally, further investigation of cell- and alginate matrix structure was accomplished using scanning electron microscopy (SEM). To study capsule properties and cell survival, osteosarcoma cells were utilized as model cells. The main objective was to study bead stability, and how the beads and the cells within were affected by the enzymatic mineralization method. Alginate beads proved to be unstable and needed addition of CaCl2 for stabilization purposes. Furthermore, in order to recover cells, citrate was added to the cell/bead suspension. Initially, results were unsatisfactory, as little, or no, RNA was recovered. After optimizing the citrate treatment it was discovered that a sequential method needed to be utilized. Results demonstrated a successful recovery of cells, and RNA of excellent quality.Enzymatic mineralization of alginate beads was found to be a cell friendly way of mineralizing alginate beads. Mineralization of beads was observed in the light microscope, by visual inspection, as well as by SEM. Cell viability remained high when using a concentration of 0.25mg/ml ALP. The osteosarcoma cells proved to be good for optimizing the enzymatic mineralization method, but behaved differently compared with mesenchymal stem cells in terms of viability, and mineralization activity. Furthermore, mineralization of beads by addition of 0.25 mg/mL ALP compared with 0.5mg/mL appeared to be beneficial as image acquisition on CLSM was facilitated and slightly higher viability of cells was observed.In the second part of the present study, human MSCs were encapsulated into alginate beads. After initial experiments the optimal condition for cell survival, and bead stability was determined. Consequently, in the final experiment 16 million MSCs were encapsulated in beads containing 0.25mg/mL ALP, together with a sample without addition of ALP. At day 2 post encapsulation both samples were divided into two batches, one cultured in regular medium, and one in differentiation medium. All samples were stabilized with 7.5 mM of CaCl2.Observations in both light microscope and CLSM revealed that only beads given ALP were mineralized before reaching day 21. At day 21 the sample receiving no ALP, cultured in differentiation medium also appeared mineralized.Mesenchymal stem cells receiving differentiation medium were observed to differentiate into mature osteoblasts in the beads. This was verified by gene expression analysis, cell morphology studies, the presence of collagen in beads seen by SEM and analysis of ALP activity. Metabolic activity measurements confirmed little cell proliferation, nor cell death. However, an increased metabolic activity was observed for encapsulated cells cultured in regular medium relative to cells in differentiation medium. Cell morphology in differentiated samples was recognized by showing elongated actin filaments, compared with the ones cultured in regular medium, which appeared round in shape. The elongated filaments suggest that the cells are able to interact with the alginate matrix and/or minerals. The occurrence of collagen fibers in SEM images further confirmed presence of mature osteoblasts. Samples cultured in regular medium with or without added ALP both showed an increase in osterix expression until day 21 when the study was ended. This was surprising, as it inferred that the alginate matrix itself might influence differentiation of MSCs into osteoblasts, and that the minerals have little effect on differentiation. Runx2 expression was detected in all samples, including unencapsulated hMSCs. The expression of runx2 was at its maximum on day 21, when the study was ended.Encapsulating mesenchymal stem cells into alginate beads mineralized by the enzymatic method is cell friendly, and allows the cells to differentiate into mature osteoblasts when cultured in differentiation medium. Alginate without minerals seems to influence differentiation to a certain extent, suggesting that minerals are not needed for differentiation to occur. The minerals do, nonetheless, speed up the continuing mineralization process.

Saccharomyces cerevisiae, commonly known as Baker’s yeast, is a eukaryotic model organism widely used in biotechnology research. Its genome has a high degree of similarity to humans, and research done on S. cerevisiae can give us a better understanding of the mechanisms involved and the cellular responses to anti-cancer drugs. Yeast is therefore usefool in increasing the effectiveness of anti-cancer drugs.The main goal for this master thesis was to investigate the metabolic response of S. cerevisiae to DNA damaging compounds. Methods for cultivation of S. cerevisiae in shake flasks or in a bioreactor, for sampling and extraction of cells, and for analysis of the sample using GC – MS were developed. A custom Deconvolution Reporting Software library was created, and used to analyze the metabolic response of S. cerevisiae to 5-fluoruracil (5FU), a widely used anti-cancer drugs. The publicly available software FiatFlux 1.6X was used for metabolic flux analysis of S. cerevisiae grown in medium containing labeled [U-13C]-glucose and in the presence of 5-fluorouracil or methyl methanesulfonate (MMS), a model alkylating agent.An overall decrease in the amount of intracellular metabolites was observed as a response to addition of a growth-inhibiting dose of 5FU, while no clear response was observed for a lower, more tolerable dose. Growth of S. cerevisiae under the presence of 5FU resulted in a different cellular response than growth under the presence of MMS. The presence of both DNA-damaging agents resulted in a decrease in the ratio of the fluxes leading to mitochondrial acetyl-CoA compared to an unstressed culture, possibly indicating a reduction in the activity of the TCA cycle. The 5FU stressed cells showed an increase in conversion of fumarate to oxaloacetate and the subsequent export out of the mitochondrion, while the MMS stressed cells showed a decrease of this flux.The experimental methods can be further refined to obtain data of higher quality, and thus allow a more complete metabolic profile to be created. The conditions for derivatization can be optimized to ensure a complete derivatization of all metabolites, the DRS library can be expanded to include a wider range of metabolites, and experiments of stressing the cells performed in a chemostat can eliminate any effects the differences in specific growth rates might have on the metabolome or fluxome of S.cerevisiae.

Produksjon av aminosyrer ved hjelp av industriell bioteknologi er et voksende marked. I dag finnes det ingen kjente metylotrofe bakterier som benyttes til industriell produksjon av aminosyrer, men en attraktiv kandidat for framtidig produksjon er den termofile og metylotrofe bakterien Bacillus methanolicus.For å kunne utvikle en konkurransedyktig produksjonsstamme av B. methanolicus er det nødvendig med genetiske verktøy. Et viktig verktøy er et reportergen som blant annet kan utnyttes for å analysere promotere. Et av hovedformålene med denne oppgaven var å teste reportergenet lacZ som stammer fra den termotolerante bakterien B. coagulans, og deretter utvikle et assay for bestemmelse av aktiviteten til genproduktet β-galaktosidase. Dette reportergenet ble også brukt til å analysere styrken til ulike promotere i B. methanolicus MGA3. Promotorene som ble undersøkt (som også stammet fra B. methanolicus) var promotere til viktige gen i metanolassimileringen (mdhp og pfkp) og den potensielle promoterregionen til et metanoldehydrogenase-gen (mdh2p). I tillegg ble det testet en kobberinduserbar promotor (Cup) fra Lactobacillus sakei. I denne oppgaven ble også det antatte replikasjonsproteinet til den potensielle vektoren pBM69 undersøkt. pBM69 ble oppdaget i B. methanolicus MGA3 etter at genomet ble sekvensert. Det ble konstruert vektorer hvor de aktuelle Promotorene var lokalisert oppstrøms for reportergenet lacZ, deretter ble B. methanolicus transformert med vektorene. Den første bekreftelsen på at reportergenet var aktivt i B. methanolicus kom under transformasjon, hvor B. methanolicus transformert med vektorene pTH1mdhp-lacZ og pTH1Cup-lacZ ga opphav til blå kolonier da kulturene ble platet ut på fast medium tilsatt X-gal. B. methanolicus transformert med pTH1mdh2p-lacZ og pTH1pfkp-lacZ ga ikke blå kolonier.Utvikling av assayet ble utført med celleekstrakt fra B. methanolicus MGA3 transformert med pTH1mdhp-lacZ. Aktiviteten ble undersøkt ved ulike betingelser for å optimere assayet. Det ble testet ulike pH-verdier for bufferen og det ble undersøkt hvordan preinkubering av enzymet påvirket aktiviteten. Den optimale pH-verdien for assayet viste seg å være rundt 7 og det ble funnet en signifikant økning i enzymaktiviteten når enzymet ble preinkubert i fem minutter ved temperaturene 45, 50 og 60 °C. Enzymaktiviteten holdt seg også stabil etter preinkubering med de gitte temperaturene i inntil 30 minutter. Etter etablering av assay ble det ved alle målingene benyttet buffer med pH 7,0 og enzymet ble preinkubert i 5 minutter ved 50 °C.Den kobberinduserbare promotoren var aktiv i B. methanolicus MGA3. For å undersøke hvordan ulike konsentrasjoner av induseren CuSO4 påvirket veksten til B. methanolicus pTH1Cup-lacZ, ble det utført forsøk hvor kulturene ble indusert med konsentrasjoner fra 0 µM til 200 µM av CuSO4. Det var tydelig at veksten ble påvirket med økende konsentrasjon av CuSO4 og ved 200 µM døde cellene. De resterende kulturene ble høstet etter hvert som OD600 = ca 1,5 og enzymaktiviteten til β-galaktosidase i hvert celleekstrakt ble bestemt. Aktiviteten for hver kultur økte med økt konsentrasjon av induser, men det var vanskelig å sammenligne aktivitetene ettersom kulturene ble høstet etter ulik inkuberingstid. I celleekstrakt fra B. methanolicus transformert med vektorene pTH1pfkp-lacZ og pTH1mdh2p-lacZ var det ikke mulig å detektere aktiviteten til β-galaktosidase. Reportergenet lacZ som ble undersøkt i denne oppgaven er det første reportergenet som har gitt gode resultater i B. methanolicus. Det etablerte assayet kan blant annet benyttes til å undersøke nye promotere i B. methanolicus og dermed øke kunnskapen om regulering av transkripsjon. Av Promotorene som ble undersøkt var mdhp den sterkeste, noe som var forventet på bakgrunn av tidligere eksperimenter. Kobberpromotoren var aktiv, men ga opphav til enzymaktivitet selv om den ikke var indusert. Det må dermed utføres flere forsøk med denne promotoren for å avgjøre hvor godt den er egnet til kontrollert ekspresjon i B. methanolicus. Replikasjonsproteinet til pBM69 ble undersøkt, men på grunn av ustabilt DNA som førte til at deler av den amplifiserte sekvensen ble slettet etter transformasjon, var det ikke mulig å bekrefte om pBM69 faktisk er et plasmid.

The uptake and incorporation of zink by a Si-, Co- , and Zn starved Thalassiosira pseudonana culture was examined. Two experiments were conducted in which a pre-determined amount of a zinc sulfate solution and sodium metasilicate nonahydrate solution were delivered to an exponentially grown fed-batch algae culture yielding the wanted start concentrations in the medium. Experiment 1 and 2 had final zinc concentration of 8.3 μM (high dose) and 1.7 μM (low dose), respectively. The experiments were conducted in batch mode for 48 hours. Frequent sampling during the first part of the experiments were performed in order to examine the biological uptake of zinc and silicate. The biological response to zinc addition was followed throughout the experiment by measuring photo-physiological parameters (Ft og QY), organic carbon and nitrogen content, cell density, optical density, and nutrient concentrations (PO43- and NO2-). The concentration development of silicate and zinc was followed in the uptake assay samples through ICP-MS analysis. The structural and elemental composition of the diatom frustules were later examined through the use of Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy, respectively. The cellular zinc development followed a two-phase sorption process in which first phase consisted of rapid metal binding to cellular surfaces followed by a gradual desorption of zinc from the cells in the second phase. High initial pH-increase followed by precipitation of zinc as hydroxides is assumed to be the main reason explaining the observed sorption trend, explicitly through the attachment of particulate zinc to cellular surfaces. Other possible explanations are assigned to complexation of zinc by organic exudates excreted from actively photosynthesizing and growing cells. Reduced biological availability of zinc may have led to decreased metal uptake by the algae. However, a higher fraction of zinc was present in the experimental frustules as compared with frustules from untreated algae culture. The highest amount of zinc was detected in the low-dose experiment corresponding to a weight-fraction relative to silicate of 5.16% for the 24 h-sample and 0.146% for the 48 h-sample. Due to the high inter-sample difference in zinc fraction combined with possible sample-contamination from chemicals or equipment through the cleaning process (H2O2) used on the frustule samples from this experiment, these fractions are connected with high uncertainty. No explicit biological response to zinc addition was observed in the algae cultures in either of the two experiments, and the reduction of the photo-physiological condition observed by the end of the experiments were related to silicate-depletion of the culture medium.

TiZir Titanium & Iron produces high titania slag and high purity pig iron from ilmenite in Tyssedal. The ilmenite is pelletized before smelting. Bentonite is added to the ilmenite concentrate as a binder to give the pellets strength and durability. Bentonite consists mainly of silica and alumina, which are considered as impurities in the high titania slag production. The use of organic binder has therefore been suggested as a substitute for bentonite.This work has focused on developing knowledge on the pelletization process and investigating various organic binders.Two methods of agglomeration, pelletization and briquetting, have been used in this work. Three batches of pellets have been made using a laboratory scale pelletizing drum. Two organic binders, Peridur 300 and Peridur 330, have been tested and compared to pellets made with bentonite and without binder. Seven batches of briquettes have been made using a cylindrical mold and a piston. Three organic binders, Peridur 300, calcium lignosulfonate and a nano cellulose fibre have been tested and compared to briquettes made with bentonite and without binder. The characterization included drop number test (pellets only), compression strength and thermal treatment.Briquettes were employed because using pellets yielded large deviations in the results. These deviations were believed to stem from the varying geometry of the pellets and were substantially mitigated by the use of cylindrical briquettes. It was found that Peridur 300 is a potential alternative to bentonite. The findings from thermal treatment suggest that above 500 degrees celcius sintering takes over as the dominating binding mechanism. For green strength, increasing binder viscosity has a positive effect.

The rare earth elements are a group of 17 elements consisting of the lantahnide series, scandium and yttrium. The application with the largest rare earth consumption is the permanent rare earth magnets. The neodymium-iron-boron magnets are the strongest permanent magnetic material known and are widely used. There is a concern that there will be a shortage in Nd-Fe-B magnets in short time. This has lead to an increased interest in the recycling of the rare earth magnets in the world.This project gives a very brief introduction to the Nd-Fe-B magnets, their uses and recycling. Two types of experiments that aims at recovery of neodymium from Nd-Fe-B magnets have been performed; extraction of neodymium by the use of molten silver and extraction of neodymium by direct oxidation. In the liquid silver experiments, extraction was obtained, but the analysis gave equivocal results. In the direct oxidation experiment, the separation of an iron phase and a neodymium oxide phase failed, and the experiment was not seen as successful.Magnetic waste from WEEE Recycling was also performed, and it turned out to contain small amounts of rare earth elements.

Lipids from marine sources contain high amounts of omega-3 fatty acids which are known to have several beneficial effects on human health. Their use as food ingredients is however limited due to their high susceptibility to lipid oxidation resulting in development of rancidity. Liposomes prepared from marine phospholipids have previously been used as a model system to study lipid oxidation by measurement of oxygen consumption. It was of interest to study lipid oxidation by this method in oil-in-water emulsions which can be considered to be more similar to foods. Incorporation of antioxidants in foods is an approach to increase the stability of foods containing omega-3 fatty acids. Emulsions were used as a model system to study the influence of EDTA, citric acid, caffeic acid, propyl gallate, α-tocopherol, ascorbic acid, β-carotene and astaxanthin on iron catalyzed lipid oxidation. Crude herring oil was washed with water to remove impurities. Analyses showed that impurities including carbonyl compounds and carotenoids were removed by the washing, while the oxidation level of the oil slightly increased. The herring oil was used for preparation of emulsions with herring phospholipids as emulsifier by the use of a dispersing tool where increased dispersing time resulted in larger oil droplets with a wider size distribution.Iron catalyzed oxidation of lipids in the emulsions occurred at a lower rate than what has previously been measured in liposomes, but the initial reaction between lipid hydroperoxides and Fe2+ occurred at the same rate in the two systems. The use of soy lecithin as emulsifier inhibited oxidation of lipids in the emulsions. Interactions between iron and antioxidants had a major impact on oxidation in the emulsions. EDTA and citric acid completely inhibited the oxidation when they were added in twice the ratio to iron. Citric acid was not able to inhibit the initial reaction between lipid hydroperoxides and Fe2+ which was thought to be due to its inability to bind Fe2+. Caffeic acid and α-tocopherol enhanced the oxidation rates by reducing Fe3+ to the more catalytically active Fe2+. The prooxidative activity of caffeic acid was significantly greater than that of α-tocopherol. Caffeic acid, α-tocopherol and propyl gallate inhibited the initial reaction between lipid hydroperoxides and Fe2+ to a similar degree which was thought to be related to their free radical scavenging and metal chelating activities. Propyl gallate was also able to reduce the oxidation rates. Ascorbic acid was itself oxidized by Fe2+ and Fe3+ which resulted in increased initial consumption of oxygen, but not increased oxidation of the lipids. Ascorbic acid was able to decrease the prooxidative activity of α-tocopherol by regeneration of α-tocopherol from the α-tocopheroxyl radical. β-Carotene and astaxanthin showed only minor influences on lipid oxidation in the emulsions.