Katalog Specialeprojektideer

Transkript

1 Katalog Specialeprojektideer Det Jordbrugsvidenskabelige Fakultet Institut for Fødevarekvalitet Kontaktperson: Aase K. Sørensen, tlf

2 Indholdsfortegnelse Metaboliske forandringer i frisk frugt og grønt efter høst...3 Sensory interaction between sweetness, sourness and bitterness and modulation of taste in vegetables...4 Changes in vitamin content and freshness in fruits and vegetables during storage...5 Bitter tasting compounds in beetroot...6 Investigation of health promoting compounds in cabbage using 1 H-NMR or LC-MS...7 Undersøgelse af indholdet og udbredelsen af bioaktive polyacetylener af falcarinoltypen i vegetabilske fødevarer...8 Interaction between different proteolytic enzyme systems in meat a hypothesis generating study...9 Kernemagnetiske resonansstudier i fødevareforskning...10 Forbud mod kastration af grise hvad gør vi så?...11 Enzymer i mælk...12 Klumper i mælk sammensætning og årsager...13 Fasting-induced adipose factor (FIAF)-inducing component in milk Effect of breeding...14 Fasting-induced adipose factor (FIAF)-inducing component in milk Effect of processing...15 Controlling milk composition by feeding...16 Protein structure - influence on the redox potential in milk and cheese quality...17 Proteins as antioxidants Effect of Protein Structure...18 Ruminal in vitro metabolism of fatty acids...19 Bioaktive peptider i mælk...20 Mælkens ostningsegenskaber...21 Kemiske og enzymatiske ændringer i flydende fødevarer ved procesbehandlinger

3 Forslag til specialeprojekter af 1 års varighed inden for: Kvalitet af frisk frugt og grønt: Metaboliske forandringer i frisk frugt og grønt efter høst Den danske forbruger efterspørger i stigende grad frisk frugt og grønt og produkter heraf, der har en høj gastronomisk kvalitet og er spiseklare eller klar til direkte brug i sandwiches, salater og forskellige varme retter. Denne form for forarbejdning stiller meget store krav til fødevareindustrien og distributører af disse produkter. Frugt og grønt er levende, hvilket bevirker at produkterne gennemgår forskellige biologiske processer efter høst, der ændrer kvaliteten. Mange af disse processer er temperaturafhængige, men selv under optimale opbevaringsforhold er det vanskeligt at bevare en høj gastronomisk kvalitet i frisk frugt og grønt. Ved at pakke frisk frugt og grønt i folie er det muligt at bevare produkternes oprindelige kvalitet i længere tid end hvis de blev opbevaret uden folie ved samme temperatur. Dette skyldes, at folien og produktet i fællesskab ændrer på luftens indhold af ilt og kuldioxid som så nedsætter de biologiske aldringsprocesser. Men dette er kun tilfældet, hvis foliens fysiske egenskaber matcher produktets behov for ilt og kuldioxid. Hvis gennemtrængeligheden af ilt og kuldioxid i folien er for høj i forhold til produktets behov, mister produktet smag og sundhedsbetydende stoffer. Omvendt bliver produktet surt, hvis gennemtrængeligheden af ilt og kuldoxid er for lav i forhold til produktets behov. Formålet med dette speciale er: at karakterisere flygtige indikatorstoffer i frisk frugt og grønt, som påvirkes af ændret ilt- og kuldioxidkoncentration at undersøge stoffernes betydning for gastronomisk kvalitet at udvikle en hurtigmetode til kvantificering af stofferne Vi kan tilbyde et speciale af et års varighed, hvor fokus er rettet på opsamling, identificering og kvantificering af potentielle flygtige stoffer fra frisk frugt og grønt opbevaret under forskellige ilt- og kuldioxidforhold. Institut for Fødevarekvalitet, Aarhus Universitet råder over metoder til dynamisk headspace-opsamling, termisk desorption samt analytisk og strukturopklarende kromatografiske metoder (GC-FID, GC-MS). Sted: Institut for Fødevarekvalitet, Fakultet for Naturvidenskab og Teknologi, Aarhus Universitet, Kirstinebjergvej 10, 5792 Årslev. Kontakt: Mere information om dette speciale fås ved henvendelse til lektor Merete Edelenbos, merete.edelenbos@agrsci.dk, tlf

4 Specialeprojekt af 1 års varighed indenfor: Sensory analysis and vegetables Sensory interaction between sweetness, sourness and bitterness and modulation of taste in vegetables Many root vegetables and cabbages contain several important bioactive phytochemicals, which seem to play a significant role for the health beneficial effects of fruits and vegetables. Several studies have suggested a correlation between high dietary phytochemical intake and a reduced risk for cardiovascular diseases. However, some of these phytochemicals like the polyacetylenes, terpenoids, glucosinolates and flavonoids are crucial for the bitter, pungent and strong taste of root vegetables and cabbages - tastes that result in dis-liking of these vegetables by many consumers. Many components such as simple sugars, minerals and other bitter blockers can interact and thus mask the bitter taste of many of these phytochemicals. This might result in higher preferences by many consumers of these vegetables. Purpose: Study the interactions between sweetness, bitterness and sourness as perceived by the human senses Study the interactions between sucrose content, mineral content, glucosinolates and bitterness of selected cabbages Methods: Sensory evaluations are carried out by a trained sensory panel The content of sucrose, glucosinolates and minerals will be performed by HPLC or atomabsorption The data will be analysed using multivariate statistical analysis Place: Dept. of Food Science, Faculty of Science and Technology, Aarhus University, Kirstinebjergvej 10, 5792 Årslev. Contact: Associate professor Ulla Kidmose, , ulla.kidmose@agrsci.dk or scientist Sidsel Jensen, , sidsel.jensen@agrsci.dk. 4

5 Changes in vitamin content and freshness in fruits and vegetables during storage It has been claimed in the ongoing public debate regarding date of expire for fresh fruits and vegetables that fruits and vegetables have a loss of vitamins during storage. Green fruits and vegetables loose their green color during storage due to break down of chlorophylls and unmasking of yellow and red carotenoids. Concomitantly with the breakdown of chlorophylls, the vitamin C content also changes. The loss of green color is affected by storage temperature, storage period and by variety. The temperature dependency regarding loss of green color is not necessarily linear e.g. the rate of loss at 5 C is different from that of 20 C. However, it is unknown how changes in vitamin A and C are related to temperature, storage period and color changes. The present study is part of the Innovationconsortium Product designed packaging of fresh fruits and vegetables. Read more on Purpose: The purpose of the master project is to study how the content of vitamins and chlorophylls and carotenoids changes in fresh fruits and vegetables during storage and to relate these changes to visual quality aspects and health issues. Phases in the study (changes can be discussed with the student): Determine which model products to work on (e.g. rocket salad and/or broccoli) Carry out a literature survey on the selected products Design storage experiments in climate chambers Conduct storage experiments with focus on respiration measures and changes in visual colour and product freshness Carry out extraction and HPLC determination of chlorophylls and carotenoids and vitamin C analysis Analyse changes in chlorophylls, carotenoids, vitamin A and C in relation to storage period and storage condition (vitamin A is determined from the HPLC analysis of carotenoids) Correlate data of the above described parameters with development in product freshness Write thesis Working period at Aarslev: The main experiment with vegetables will take place from 1 st of August 1 st of November 2011, so the practical part of the present study should be within this time frame. Afterwards, there will be meetings at Aarslev and Aarhus. Place: Project group: Dept. of Food Science, Faculty of Science and Technology, Aarhus University, Kirstinebjergvej 10, 5792 Årslev. The project will be carried out in close cooperation with postdoc Helene Fast Seefeldt and associate professor Merete Edelenbos. Contact: Postdoc Helene Fast Seefeldt , helenef.seefeldt@agrsci.dk or associate professor Merete Edelenbos , med@agrsci.dk. 5

6 Bitter tasting compounds in beetroot In recent years, Nordic gastronomy has become very popular, and the interest in root vegetables has increased. Beetroot is a traditional Danish root vegetable and especially the red, long type is used in the kitchens. But beetroot exist in a large variety of shapes and colors which are not fully exploited. Increased knowledge on the sensory quality and chemical composition of these can increase the preference and consumption of beetroots by consumers. Earlier performed sensory and consumer evaluation of beetroots have shown differences between varieties in sweetness, bitter taste and astringency. The bitter taste of beetroot is mainly due to the content of polyphenols, and astringency is normally caused by tannins. Beetroot is one of the vegetables with the highest content of polyphenols, but knowledge about the polyphenol composition has never been thoroughly investigated in order to relate it to the taste and quality of beetroots. The master project will be a part of the ongoing research project Gourmet Roots ( See more about the different beetroots at: Purpose The purpose of this master project is to investigate changes in the content of polyphenols and sugars in beetroot during culinary preparation and between different varieties. Contents Perform a literature study on bitter tasting compounds in beetroot Develop and optimize extraction procedures from beetroot material Develop a method for analyzing sugars and different polyphenols in beetroot using HPLC Determine the content of sugars and chosen polyphenols in raw and boiled beetroots of different varieties Relate the results to the sensory quality of the beetroots Place: Project group: Contact: Dept. of Food Science, Fyn, Faculty of Science and Technology, University of Aarhus, Kirstinebjergvej 10, 5792 Årslev. The project will be carried out in close cooperation with PhD-student Vibe Bach and associate professor Merete Edelenbos Associate professor Merete Edelenbos , med@agrsci.dk or PhD student Vibe Bach, , vibe.bach@agrsci.dk. 6

7 Investigation of health promoting compounds in cabbage using 1 H-NMR or LC-MS In this project, cabbage of different varieties has been grown under conditions directed for an increased content of secondary metabolites. Because the health promoting effects of cabbage and roots are believed to be mediated by these compounds, it is highly relevant to investigate the effects of growth conditions and variety on the plant metabolite profile. This would provide us with valuable information about the health-potential of different varieties and the optimal conditions for the formation of these compounds. Furthermore, the sensory properties of the plants are of major importance and the results obtained in this project will be linked to sensory evaluations of the plants. The experimental work will to a large extent depend on the interests of the student and could include: Optimization of extraction methods 1 H-NMR based metabonomic investigation with emphasis on the variety and growth condition effects in cabbage Investigation of 1 H-NMR methods suited for analysis of secondary metabolites in cabbage New methods for improved assignment of 1 H-NMR spectra Mass spectrometry-based profiling of metabolites Hands-on experience with the mentioned methods is not a requirement. Contact: Post doc Morten Rahr Clausen, Dept. of Food Science, Faculty of Science and Technology, Aarhus University, Kirstinebjergvej 10, 5792 Årslev , mortenr.clausen@agrsci.dk. 7

8 Forslag til specialeprojekter af 1 års varighed inden for: Bioaktive naturstoffer Undersøgelse af indholdet og udbredelsen af bioaktive polyacetylener af falcarinol-typen i vegetabilske fødevarer Polyacetylener af falcarinol-typen er meget interessante bioaktive stoffer i grøntsager, der tilhører skærmplantefamilien så som gulerødder, selleri, bladselleri og persille etc. Disse polyacetylener har vist immunstimulerende og anti-inflammatorisk effekt og en forebyggende effekt mod udvikling af hjerte- karsygdomme og ikke mindst kræft. Disse stoffer anses derfor som vigtige i forhold til at kunne forklare nogle af de sundhedsgavnlige effekter af grøntsager fra skærmplantefamilien. Der er kun lavet meget få undersøgelser om udbredelsen af polyacetylener af falcarinol-typen i grøntsager og det er derfor vigtigt at få bestemt indholdet og variationen af disse stoffer i de nævnte grøntsager for at kunne bestemme det daglige indtag af disse forbindelser. Endelig vil det være yderst interessant om nogle af disse grøntsager indeholder nye polyacetylener med endnu ikke klarlagt biologisk aktivitet. Vi kan derfor tilbyde et speciale, hvor en lang række grøntsager fra skærmplantefamilien undersøges for indhold af bioaktive polyacetylener samt evt. isolering og identifikation af nye polyacetylener. Polyacetylener kvantificeres i planteekstrakter vha. analytisk HPLC og isoleres ved kolonnekromatografi og præparativ HPLC og identificeres ved 1D- og 2D-NMR og massespektrometri. Kontakt: Mere information om dette speciale kan fås ved henvendelse til seniorforsker Erik Larsen, Institut for Fødevarekvalitet, Fakultet for Naturvidenskab og Teknologi, Aarhus Universitet, Kirstinebjergvej 10, 5792 Årslev. erik.larsen@agrsci.dk, tlf

9 Kød: Interaction between different proteolytic enzyme systems in meat a hypothesis generating study Naturally occurring proteases in muscles are important for the tenderization process in meat, even though their original function is in the regulation of protein turnover in the living muscle. The Ca 2+ dependent calpain system is suggested to initiate the protein degradation in vivo and post mortem tenderization, but also other proteases seem to be involved in the degradation of muscle proteins post mortem, such as the lysosomal cathepsins and the proteasome complex. Recently, we presented results that indicate a sequential degradation of the structural proteins post mortem, where the calpains initiate the disruption and destabilisation of the myofibrillar structure, and thereby allow the proteasome complex to act. However, the interaction between the proteolytic enzyme systems is not described in detail. The different enzymes have very different ph optima, which is very decisive for the post mortem protease activities in meat, and the interaction between the calpain system, the proteasome complex and the cathepsins should therefore be characterised with ph as one of the variables. Purpose: Characterisation of the hydrolysates formed after enzymatic hydrolysis of muscle proteins by the calpains found in meat Characterisation of the hydrolysates formed after enzymatic hydrolysis of muscle proteins by the proteasome complex Characterisation of the hydrolysates formed after enzymatic hydrolysis of muscle proteins by the cathepsins Quantification of the release of peptides from - the calpain digest - the proteasome digest - the cathepsins digest - the calpains + the proteasome + the cathepsins digest Generate hypothesis for possible interactions between proteolytic enzymes involved in post mortem tenderisation of meat Methods: Characterisation/quantification of the hydrolysates is performed by: LC-MS (ES) MALDI TOF-TOF SDS page Western blotting Place: Dept. of Food Science, Faculty of Science and Technology, University of Aarhus, Blichers Allé 20, 8830 Tjele. Contact: Associate professor Margrethe Therkilsen, , Margrethe.Therkildsen@ agrsci.dk or scientist Trine Kastrup Dalsgaard, , Trine.Dalsgaard@agrsci.dk. 9

10 Kernemagnetiske resonansstudier i fødevareforskning Kernemagnetisk resonans (NMR) er en spektroskopisk metode, hvor kernernes magnetiske egenskaber udnyttes til at opnå information om fysiske og kemiske karakteristika. Således kan NMR for eksempel anvendes til at kigge på vandfordeling eller til at studere fedtkrystallisation i fødevarer. Stofsammensætningen i blod og urin kan også analyseres ved hjælp af NMR, og således kan NMR også bruges til at undersøge, hvordan kroppen reagerer på indtagelse af forskellige fødevarer. Der er mange anvendelsesmuligheder af NMR og i projektet vil der både være mulighed for at undersøge dynamiske processer i fødevarer og at udvikle nye metoder til at undersøge fødevarer. Alt afhængig af dine interesser vil vi meget gerne skrue et projekt sammen, der passer til dig. Eksempler på projekter: Dynamiske processer i fødevarer Vandfordeling i kød under frysning og manipulering af vands frysepunkt i kød ved salttilsætning Påvirkning af mælkefedtkrystallisationens temperatur ved tilsætning af forskellige komponenter Undersøge de biokemiske effekter når man fodrer grise med gulerødder NMR-metoder Udvikling af metoder til detektion af strukturgivende polymerer i grøntsager og deres relation til sensorisk kvalitet NMR-baseret hurtigmetode til kvantificering af plantemetabolitter Udvikling og anvendelse af to-dimensionelle NMR-metoder. Sted: Institut for Fødevarekvalitet, Fakultet for Naturvidenskab og Teknologi, Aarhus Universitet, Kirstinebjergvej 10, 5792 Årslev. Kontakt: Seniorforsker Hanne C. Bertram, , HanneC.Bertram@agrsci.dk, eller forsker Morten Rahr Clausen, , MortenR.Clausen@agrsci.dk. 10

11 Forbud mod kastration af grise hvad gør vi så? I Danmark produceres årligt ca. 25 millioner svin, hvoraf millioner er hangrise, der kastreres uden bedøvelse indenfor de første 2 til 7 dage af deres liv. Grunden til, at de kastreres, er, at man derved undgår at grisen ved slagtning har udviklet ornelugt og derved forringet kødkvalitet. Ornelugt skyldes to kemiske stoffer nemlig skatol og androstenon. Skatol produceres i tarmen på grisen og optages i blodbanen og nedbrydes i leveren af enzymer (cytochrome P450). Androstenon produceres i grisens testikler og nedbrydes også i leveren. Problemet med ornelugt opstår, hvis nedbrydningen ikke er stor nok. Androstenon har en hæmmende effekt på skatol-nedbrydningen og derfor bruger man kastration som et middel mod ornelugt. Planten cikorie har vist sig, iblandet foderet, at være effektiv til at mindske den mængde skatol, der bliver dannet i tarmen, og derved den mængde der optages i grisen. Vi har endvidere grund til at tro, at cikorie har langt flere gavnlige effekter, nemlig ved at øge mængden og aktiviteten af skatol og androstenon-nedbrydende enzymer. Der tilbydes to specialeprojekter (såfremt der opnås midler til projekt 2). Projekt 1: Formål: Undersøge reguleringen af transskriptionen af cytochromer i primære leverceller fra grise. Dette gøres i henhold til steroider, skatol, androstenon og cikorie. Metode: Dyrke primære leverceller og stimulere disse forskellige steroider o.l. Responset undersøges på mrna niveau. Projekt 2: Formål: Undersøge cikories påvirkning på mængden og aktiviteten af specifikke cytochromer i leveren hos grise. Metode: I et fodringsforsøg gives til en gruppe grise tørret cikorie i 2 uger før slagtning. Til at undersøge enzymmængden bruges Western blotting, mens enzymaktiviteten undersøges ved brug af specifikke substrater (og HPLC). Sted: Institut for Fødevarekvalitet, Fakultet for Naturvidenskab og Teknologi, Aarhus Universitet, Blichers Allé 20, Postboks 50, 8830 Tjele. For mere information kontakt: Ph.d.-studerende Martin Krøyer Rasmussen, Tlf , Martink.rasmussen@agrsci.dk eller Seniorforsker Bo Ekstrand. Tlf , Bo.Ekstrand@agrsci.dk. 11

12 Mælk: Enzymer i mælk Formål: At identificere kvalitetsforringende enzymer og proteolyseprodukter i mælk med forskelligt celletal. Baggrund: Der findes en række proteolytiske enzymer i mælk, der kan nedbryde mælkens proteiner. Det er en ønsket proces under f.eks. ostemodning, mens det er uønsket i den rå mælk og i ostemælk, da det kan medføre en forringet holdbarhed af mælk, lavere osteudbytte og påvirke produktkvaliteten. Man kender en del af disse kvalitetsforringende enzymer, men ikke alle er identificeret. For en del af disse ved man, at indholdet og aktiviteten af enzymerne stiger i mælken ved stigende celletal, og dermed er associeret med yversundheden. På koniveau kan der mellem forskellige kirtler være stor forskel på både celletallet og sammensætningen af de celler, som celletallet dækker over. Ved at karakterisere hvilke nedbrydningsprodukter, der er dannet i mælken fra forskellige kirtler, kan man pege på hvilke enzymer, der har været ansvarlige, og dermed vurdere sammenhæng mellem celletal, yversundhed, specifikke enzymer og mælkekvalitet. Indhold: Proteolyseprodukter karakteriseres i mælk med forskelligt celletal ved brug af LC MALDI spotting. Ved brug af kapillar HPLC fraktioneres peptider fra mælk og spottes direkte på target til MALDI-TOF massespektrometri. Ved MS kan disse peptider identificeres, og ved databasesøgninger også hvorfra de er dannet. Gennem identifikation af spaltningssteder kan der kommes med forslag til hvilke kvalitetsforringende enzymer, der har været på spil. Der kan endvidere anvendes proteomanalyse til karakterisering af mælkens proteinkvalitet ved forskelligt celletal ved analyse af proteinnedbrydningen gennem proteinseparation på todimensionelle geler, udpegning af hot-spots og identifikation af proteiner og fragmenter ved MALDI-TOF. Resultatet bruges til at pege på betydningen af celletal for mælkens sammensætning og proteinnedbrydning. De kvalitetsforringende enzymer i mælk med forskelligt celletal kan endvidere karakteriseres ved enzymatiske tests, immunoblots, og nye enzymer søges identificeret ved integration af antistof-teknikker med MALDI-TOF massespektrometri. Sted: Institut for Fødevarekvalitet, Fakultet for Naturvidenskab og Teknologi, Aarhus Universitet, Blichers Allé 20, 8830 Tjele. Kontakt: Lektor Lotte Bach Larsen, Institut for Fødevarekvalitet, tlf , lottebach.larsen@agrsci.dk. 12

13 Klumper i mælk sammensætning og årsager Formål: At belyse sammensætningen af klumper, der er dannet i mastitismælk med henblik på at identificere de mekanismer, der ligger bag, og dermed kunne udvikle sensorer, der kan frasortere denne type af mælk i malkerobotter. Baggrund: I forbindelse med mastitis dannes der ofte klumper og flager i mælken. Dannelsen af disse er et resultat af en ændret mælkesammensætning ved mastitis. Der sker en stigning i antallet af leucocytter, og andelen af valleprotein stiger, herunder også mængden af immunoglobulin. Også forholdet mellem frit og micel-bundet kasein forskydes mod en større andel af frit kasein. Ligeledes stiger en række af mælkens enzymer, bl.a. de proteolytiske, og dermed stiger proteolysen af kaseinerne i denne type mælk. Der kan være flere årsager til dannelsen af klumper og flager i mastitismælk. Det kan f.eks. skyldes agglutinering af immunoblobulin, valleprotein og fedtkugler, men også proteolyse af kaseinerne med efterfølgende aggregering er en mulighed. Det er påvist, at der findes para-κ-kasein i visse typer af mastitismælk: det fragment, der dannes fra κ-kasein i forbindelse med ostefremstilling efter tilsætning af chymosin eller osteløbe. Det er ligeledes vist, at nogle af de enzymer, der stiger i mælk i forbindelse med mastitis, er i stand til naturligt af spalte κ-kasein på denne måde. Det er derfor nærliggende at forestille sig, at mælkens enzymapparat kan spille en rolle i dannelsen af disse uønskede klumper og flager, men i hvor høj grad det sker, er ukendt på nuværende tidspunkt. Mælk, der er visuelt forandret, skal frasorteres under malkningen, da det ikke må leveres til mejeriet. Traditionelt har man anvendt den visuelle bedømmelse af formælk, men i forbindelse med indførelsen af malkerobotter (automatisk malkning, AMS) er det blevet tvingende nødvendigt af finde alternativer til den visuelle bedømmelse. Projektet er derfor en del af et større projekt, hvor formålet på længere sigt er at opstille målealgoritmer for forandret mælk, og dermed at kunne fremstille sensorer, der med større nøjagtighed end i dag kan frasortere forandret mælk. Projektet udføres i samarbejde med forskere fra Institut For Husdyrsundhed, Velfærd og Ernæring og fra Institut for Jordbrugsteknik. Indhold: Den overordnede sammensætning (fedt, protein og laktose) af forskellige typer af klumper bestemmes ved forskellige metoder. Klumperne isoleres fra mælk fra dyr på forskellige infektionsstadier. Klumperne inddeles efter om de hovedsageligt består af fedt eller protein. Derefter bestemmes deres detailsammensætning ved brug af forskellige metoder, som GC-MS og state-of-the-art proteomicsmetoder. Klumpernes sammensætning analyseres ved 2- dimensionel gel elektroforese, samt ved multidimensionel kapillar HPLC af proteiner og peptider. Begge metoder er koblet op på proteindetektion ved brug af massespektrometri. Endvidere skal der anvendes forskellige assays til detektion af proteolyse og proteolytiske enzymer. Det kan også komme på tale at anvende immunologiske metoder til detektion af enzymer. Sted: Institut for Fødevarekvalitet, Fakultet for Naturvidenskab og Teknologi, Aarhus Universitet, Blichers Allé 20, 8830 Tjele. Projektet udføres i samarbejde med forskere fra andre institutter ved DJF. Kontakt: Lektor Lotte Bach Larsen, Institut for Fødevarekvalitet, tlf , lottebach. larsen@agrsci.dk. 13

14 Fasting-induced adipose factor (FIAF)-inducing component in milk Effect of breeding Recent studies have suggested that milk and milk products can regulate weight. Different mechanisms behind this have been investigated and one suggestion is that milk contains weight regulating components, which may diminish uptake of lipids from the intestine, reduce uptake into fat cells and/or increase lipid oxidation. In preliminary experiments, we have for the first time found a fasting-induced adipose factor (FIAF)-inducing component in milk, which at least in part may explain the adiposity-reducing effect of milk. It has been shown that increased levels of FIAF in circulation suppresses lipoprotein lipase (LPL) and thereby lipid uptake by target organs. FIAF was identified as a factor secreted from the adipose tissue, but it is also produced in the liver and the intestinal mucosa. The gut microbiota has been shown to inhibit expression and secretion of FIAF leading to enhanced accumulation of fat in adipose tissue. Recent study in our laboratory has shown that the FIAF gene (also named Angptl4) expression in the intestinal cell is dependent on the fat content of milk. We also know that there is a difference in fat content and size of the fat globules between for example Jersey and Danish Holsteins. The purpose of the present study is to investigate the impact of breeding on the expression on the FIAF gene in human intestinal cells. In this project, you learn to work with human cell cultures, get an insight into how milk can affect the uptake of nutrients in the gut and furthermore become familiar with breeding of Danish dairy cows. Place: The study will be performed at Department of Food Science, Faculty of Science and Technology, Aarhus University, Blichers Allé 20, Foulum, 8830 Tjele. For more information contact: Associate professor Jette F. Young jettef.young@agrsci.dk, Scientist Trine K. Dalsgaard ( ) trine.dalsgaard@agrsci.dk or Head of Research Unit Grith Mortensen ( ) grith.mortensen@agrsci.dk This master project will be a part of a larger project; FIAF: Milk in regulating lipid metabolism and overweight. Uncovering milk s ability to increase expression and activity of fasting-induced adipose factor, which is performed in collaboration with Arla Foods, The Danish Dairy Board, KU-Biology, KU-Human Nutrition, AU-MAPP, AU-animal science, NIFES, and UG-CMR. 14

15 Fasting-induced adipose factor (FIAF)-inducing component in milk Effect of processing Recent studies have suggested that milk and milk products can regulate weight. Different mechanisms behind this have been investigated and one suggestion is that milk contains weight regulating components, which may diminish uptake of lipids from the intestine, reduce uptake into fat cells and/or increase lipid oxidation. In preliminary experiments, we have for the first time found a fasting-induced adipose factor (FIAF)-inducing component in milk, which at least in part may explain the adiposity-reducing effect of milk. It has been shown that increased levels of FIAF in circulation suppresses lipoprotein lipase (LPL) and thereby lipid uptake by target organs. FIAF was identified as a factor secreted from the adipose tissue, but it is also produced in the liver and the intestinal mucosa. The gut microbiota has been shown to inhibit expression and secretion of FIAF leading to enhanced accumulation of fat in adipose tissue. In our laboratory, it was recently shown that the FIAF gene (also named Angptl4) expression in the intestinal cell is dependent on the fat content of milk, but we will like to investigate the effect of processing as well. Thus, the purpose of the present study is to investigate the impact of milk processing on the expression on the FIAF gene in human intestinal cells. In this project you will become familiar with: different processing techniques that are normally used in the dairy industry working with human cell cultures and furthermore get an insight into how milk can affect the uptake of nutrients in the gut Place: The study will be performed at Department of Food Science, Faculty of Science and Technology, Aarhus University, Blichers Allé 20, 8830 Tjele. For more information contact: Associate professor Jette F. Young jettef.young@agrsci.dk, Scientist Trine K. Dalsgaard ( ) trine.dalsgaard@agrsci.dk or Head of Research Unit Grith Mortensen ( ) grith.mortensen@agrsci.dk This master project will be a part of a larger project; FIAF: Milk in regulating lipid metabolism and overweight. Uncovering milk s ability to increase expression and activity of fasting-induced adipose factor, which is performed in collaboration with Arla Foods, The Danish Dairy Board, KU-Biology, KU-Human Nutrition, AU-MAPP, AU-animal science, NIFES, and UG-CMR. 15

16 Controlling milk composition by feeding The technological and nutritional quality of milk is affected by feed composition and especially fatty acid composition and milk content of antioxidants are affected. Feeding high amounts of grass products increases the milk content of polyunsaturated fatty acids as well as the content of tocopherols and carotenoids. Milk with higher content of polyunsaturated fatty acids is more liable to oxidation; however, a higher content of antioxidants may delay this oxidation. The purpose of the project is to collect milk from a range of cows where feeding details are known. Cows from the Science and Technology Faculty herd in Foulum or cows from the Danish Cattle Research Centre in Foulum may be used for the project, but milk from private farms may also be included as appropriate. This milk should be analysed for fatty acid composition as well as content of antioxidants. Transfer of other compounds from feed to milk may be studied as well. The oxidative stability of some milk types could be analysed and especially the relation between tocopherol content and oxidation may be studied as tocopherol may act as an antioxidant in early oxidation and a prooxidant in severe oxidation. Other aspects may be studied depending on the ongoing projects at Faculty of Science and Technology. Place: Department of Food Science, Faculty of Science and Technology, Aarhus University, Blichers Allé 20, Postboks 50, 8830 Tjele Contact: Scientist Mette Krogh Larsen, tel mette.larsen@agrsci.dk. 16

17 Protein structure - influence on the redox potential in milk and cheese quality If you have an interest in working with model systems and to verify the obtained knowledge in real dairy products, this might be the master project for you. In this project, you will look at protein structure in relation to their redox potential both in model systems and in milk and elucidate its impact on coagulation properties in relation to cheese quality. Background Empirical cheese production trials have proved that the use of vacuumized milk leads to a better acidification process, improved flavor profiles, and more uniform products. The removal of oxygen from the milk has a high impact on the redox potential (E h ), which again affects the microbial growth, and thus the starter culture. However, the technological insight into the E h and its effect on cheese quality is still limited. The typical E h in milk is approx mv. The milking method, mechanical stress (pumping, etc.), and storage may affect the E h. Furthermore, heat treatment and reduction of oxygen in the milk by vacuum treatment at the dairy plant are expected to affect the E h. However, studies indicate that milk proteins may have impact on the redox potential as well. Objectives The objective of the present study is to describe the influence of various heat treatments on the redox potential in model systems with α-lactalbumin, β-lactoglobulin and bovine serum albumin (BSA). In order to illustrate how SH-groups affect the redox potential, the experiments will be repeated with N-ethylmaleimide (NEM), which blocks free SH-groups. The findings in model systems can subsequently be tested in milk where coagulation properties can be evaluated. Methods Redox potential electrode Differential Scanning Calorimetry (DSC) to measure changes of protein denaturation profile Fluorescence spectroscopy to measure changes in protein folding Quantification of the number of free SH groups Coagulation by ReoRox-measurements Place: Department of Food Science, Faculty of Science and Technology, Aarhus University, Blichers Allé 20, Foulum, 8830 Tjele. Collaborators: This master project will be a part of a larger project; Redox potential in milk the influence on cheese quality, which is performed in collaboration with Arla Foods, Thise Dairy, Chr. Hansen s and KU-Life (Food Microbiology). For further information please contact: PhD student Else Vesterlund, , Else.Vesterlund@agrsci.dk, Scientist Trine Kastrup Dalsgaard, , Trine.Dalsgaard@agrsci.dk or Head of research unit Grith Mortensen, , Grith.Mortensen@agrsci.dk. 17

18 Proteins as antioxidants Effect of Protein Structure Oxidative deterioration is a major problem for the food industry due to reduced nutritious quality, formation of off-flavors and changed functionality. In a globalized market, shelf-life and oxidatively stable products based on natural antioxidants have high priority. Empiric studies have shown that proteins have potential as antioxidants in foods. However, today the use of proteins as antioxidants has not been an issue for the industry. This may be due to the fact that the mechanism behind the antioxidative activity of the proteins is poorly understood, and that a strategic use of proteins as antioxidants is conditional on the mechanism of the antioxidative activity being well understood. In order to design an antioxidant consisting of proteins, that is optimized for a specific food system where one of the oxidation mechanisms i) photooxidation, ii) metal-mediated, or iii) enzyme-catalyzed oxidation is dominating, the present study will use a scientific approach to understand the importance of protein structure, amino acid composition and oxidation mechanisms in relation to the antioxidative activity of proteins. The objective of the present study is to understand the mechanism behind the way proteins act as antioxidants and show the dependence of protein structure in that context. In this project you will learn a unique method to detect free radicals in different molecules measure free radicals in proteins and other molecules detect radical transfer between molecules understand and verify the nature of different radicals look at changes in protein structure upon oxidation Methods Different spectroscopy methods (e.g. electron spin resonance (ESR), fluorescence spectroscopy). For more information contact: Scientist Trine K. Dalsgaard ( ), trine.dalsgaard@ agrsci.dk. The study will be performed at Department of Food Science, Faculty of Science and Technology, Blichers Allé, Foulum, 8830 Tjele, Aarhus University. 18

19 Ruminal in vitro metabolism of fatty acids Background: Milk fatty acid composition, as well as other milk components, may be controlled by feeding. However, the effects of different types of feed are to a wide extent due to effects on rumen metabolism rather than direct transfer of feed fatty acids to milk. Due to these mechanisms it is relevant to study how feed components affect rumen metabolism. This is mainly done by incubating feed components and rumen liquid in an in vitro system. The rumen is a complex ecosystem of microorganisms and any external influence, such as antimicrobial substances, will affect rumen metabolism with changes in milk fatty acid composition, methane production and animal growth as possible consequences. In 2006, the European Union banned the use of antibiotics for this purpose, increasing the need for natural ways to modify rumen metabolism. Purpose: The changes in fatty acid composition, volatile compounds and methane production should be studied on ruminal processes in vitro. Experiments should be based on silage, fresh grass and a variety of plant-based additives, such as oregano, thyme, ginger and other plants known to have antimicrobial properties. Results should lead to attempts to isolate active substances and suggest recommendations for use of feed additives to improve milk fatty acid composition and reduce methane emission. Methods: In vitro incubation, GC, GC-MS. Place: Dept. of Food Science, Faculty of Science and Technology, Aarhus University, Blichers Allé 20, 8830 Tjele. The project will be working closely together with a PhD project within the same area. Contact: Scientist Mette Krogh Larsen , mette.larsen@agrsci.dk or PhD student Johan Lejonklev, , JohanS.Lejonklev@agrsci.dk. 19

20 Bioaktive peptider i mælk Mælk indeholder mange proteiner, der fordøjes når mælken eller mejeriprodukter indtages. Derved hydrolyseres bl.a. mælkens kaseindel, og der kan frigives bioaktive peptider. Vi har et veletableret samarbejde med forskere fra Institut for Husdyrbiologi og Sundhed (Animal Science) omkring test af bioaktive peptider i modeller for sårheling. Vi producerer hydrolysater af kaseiner i laboratoriet og tester deres bioaktivitet i cellemodeller for sårheling i mave-tarmkanalen og i hudceller (epithelceller og keratinocytter). Bioaktive preparationer kan derefter karakteriseres ved forskellige fraktoneringsmetoder og ved brug af massespektrometri (MS) i peptidomics studier for at komme nærmere de bioaktive komponenter. Formål: Fremstille hydrolysater af mælkeprotein og teste disse i modeller for sårheling og derefter karakterisere aktive preparationer. Metode: Tilsætte fordøjelsesenzymer til mælkeprotein, tilsætte disse til celler i kultur og teste for cellemigration og proliferation. Til at karakterisere aktive preparationer anvendes HPLC koblet med MS. Sted: Institut for Fødevarekvalitet og Institut for Husdyrbiologi og Sundhed (Animal Science), Fakultet for Naturvidenskab og Teknologi, Blichers Allé 20, Postboks 50, 8830 Tjele. Institut for Fødevarekvalitet har ca. 25 speciale- og Ph.d.-studerende, som alle vægter det sociale såvel som det faglige højt. Der afholdes bl.a. et årligt seminar, som alle specialestuderende tilbydes at deltage i, samt uformelle frokostmøder. For mere information kontakt: Lektor Lotte Bach Larsen, Tlf , 20

21 Mælkens ostningsegenskaber Mælkens ostningsegenskaber er en meget vigtig teknologisk parameter for mejerierne. Mælkens ostningsevne eller koaguleringsegenskaber er afgørende for både osteudbytte, modningsforløbet og kvaliteten af de færdige oste. I koaguleringens første fase spaltes mælkens κ- kasein efter tilsætning af osteløbe enzymet. Vi har gennem flere projekter studeret variationer i ostningsevne af mælk fra forskellige køer, og har opnået en del viden i det område. Specialet vil derfor omhandle en nærmere undersøgelse af sammenhænge mellem den metode vi hidtil har anvendt til karakterisering af mælkens ostningsevne (en hurtigmetode) og en mere grundlæggende rheologisk tilgang med fastlæggelse af måleomstændigheder såsom frekvens, amplitude, temperatur, m.m. og disses betydning for beskrivelse af både koaguleringsforløbet og det færdige oste-koagels kvalitet. Desuden undersøges betydningen af calcium på koaguleringsprocessen. Der vil eventuelt kunne inddrages undersøgelser af kinetikken af fraspaltningen glycomacropeptidet (GMP) i forskellige κ-kasein typer, og et samarbejde med mejeriindustrien kan eventuelt være en del af projektet. Formål: At etablere grundlæggende viden om mælkens teknologiske egenskaber og herunder at undersøge sammenhænge mellem mælkens ostningsevne og rheologiske målinger. Metode: Tilsætte osteløbe til forskellige mælkeprøver og foretage koaguleringsundersøgelser og rheologiske målinger af koaguleringsforløbet. Eventuelt kinetiske og strukturelle undersøgelser af frigivelsen af GMP fra κ-kasein ved HPLC og massespektrometri. Sted: Institut for Fødevarekvalitet, Fakultet for Naturvidenskab og Teknologi, Blichers Allé 20, Postboks 50, 8830 Tjele. Institut for Fødevarekvalitet har ca. 25 speciale- og Ph.d.-studerende, som alle vægter det sociale såvel som det faglige højt. Der er bl.a. et årligt seminar, som alle specialestuderende tilbydes at deltage i, og ugentlige uformelle frokostmøder hvor resultater og ideer fremlægges. For mere information kontakt: Lektor Lotte Bach Larsen, Tlf , lottebach.larsen@agrsci.dk og Lektor Marianne Hammershøj, Tlf , mah@agrsci.dk. 21

22 Kemiske og enzymatiske ændringer i flydende fødevarer ved procesbehandlinger SPX (APV) (ww.spxflowtechnology.com) er interesseret i samarbejde om speciale som omhandler hvorledes deres teknologiprocesser påvirker kemiske og enzymatiske reaktioner i flydende fødevarer, såsom fx mælk og ketchup. Sted: Institut for Fødevarekvalitet, Fakultet for Naturvidenskab og Teknologi, Aarhus Universitet, Blichers Allé 20, 8830 Tjele. Kontakt: Lektor Lars Wiking, lars.wiking@agrsci.dk, tlf Se de følgende sider for yderligere information: 22

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