{"id":6317,"date":"2026-10-19T09:48:45","date_gmt":"2026-10-19T09:48:45","guid":{"rendered":"https:\/\/phd.hi.is\/doktorsvorn\/doktorsvorn-i-matvaelafraedi-ragnhildur-einarsdottir\/"},"modified":"2026-10-19T09:48:45","modified_gmt":"2026-10-19T09:48:45","slug":"doktorsvorn-i-matvaelafraedi-ragnhildur-einarsdottir","status":"publish","type":"phd_defence","link":"https:\/\/phd.hi.is\/en\/doktorsvorn\/doktorsvorn-i-matvaelafraedi-ragnhildur-einarsdottir\/","title":{"rendered":"Doktorsv\u00f6rn \u00ed matv\u00e6lafr\u00e6\u00f0i – Ragnhildur Einarsd\u00f3ttir"},"content":{"rendered":"
\n
\n

F\u00f6studaginn 16. desember ver Ragnhildur Einarsd\u00f3ttir doktorsritger\u00f0 s\u00edna \u00ed matv\u00e6lafr\u00e6\u00f0i vi\u00f0 Matv\u00e6la- og n\u00e6ringarfr\u00e6\u00f0ideild H\u00e1sk\u00f3la \u00cdslands. Ritger\u00f0in ber heiti\u00f0: \u00datdr\u00e1ttur \u00e1 l\u00edfvirkum efnum \u00far st\u00f3r\u00fe\u00f6rungum me\u00f0 p\u00falsu\u00f0u rafsvi\u00f0i. \u00c1hrif st\u00e6r\u00f0ar l\u00edp\u00f3s\u00f3ma \u00e1 h\u00fa\u00f0un me\u00f0 kaldsj\u00e1varfiskigelat\u00edni. Novel extraction of bioactive compounds from macroalgae with pulsed electric field. The influence on liposomal dispersions of particle size and electrostatic deposition of cold water fish skin gelatin.<\/strong><\/p>\n

Andm\u00e6lendur eru dr. James Lyng, pr\u00f3fessor vi\u00f0 H\u00e1sk\u00f3lann \u00ed Dublin, \u00cdrlandi, og dr. Federico Gomez, pr\u00f3fessor vi\u00f0 H\u00e1sk\u00f3lann \u00ed Lundi \u00ed Sv\u00ed\u00fej\u00f3\u00f0.<\/p>\n

Umsj\u00f3narkennari var Kristberg Kristbergsson, pr\u00f3fessor, og lei\u00f0beinandi Krist\u00edn Anna \u00de\u00f3rarinsd\u00f3ttir, matv\u00e6lafr\u00e6\u00f0ingur (PhD). A\u00f0rir \u00ed doktorsnefnd voru Bj\u00f6rn Vi\u00f0ar A\u00f0albj\u00f6rnsson, lektor og Jakob Kristj\u00e1nsson, pr\u00f3fessor emeritus.<\/p>\n

Mar\u00eda Gu\u00f0j\u00f3nsd\u00f3ttir, pr\u00f3fessor og deildarforseti Matv\u00e6la- og n\u00e6ringarfr\u00e6\u00f0ideildar, stj\u00f3rnar ath\u00f6fninni sem fer fram \u00ed H\u00e1t\u00ed\u00f0asal H\u00e1sk\u00f3la \u00cdslands og hefst kl. 13.00.<\/p>\n

\u00c1grip<\/strong><\/p>\n

St\u00f3r\u00fe\u00f6rungar eru vann\u00fdtt au\u00f0lind l\u00edfvirkra efna fyrir matv\u00e6la-, snyrtiv\u00f6ru- og lyfjai\u00f0na\u00f0inn. Marka\u00f0ur er fyrir h\u00e1g\u00e6\u00f0a l\u00edfvirk efni sem hafa veri\u00f0 framleidd \u00e1 umhverfisv\u00e6nan h\u00e1tt \u00e1n l\u00edfr\u00e6nna leysa. \u00datdr\u00e1ttur me\u00f0 h\u00e1spennu-rafp\u00falsum (PEF) er \u00e1litleg a\u00f0fer\u00f0 \u00fear sem hvorki er nota\u00f0ur h\u00e1r hiti n\u00e9 mikil orka. L\u00edti\u00f0 hefur veri\u00f0 fjalla\u00f0 um notkun PEF \u00e1 st\u00f3r\u00fe\u00f6runga. H\u00e6gt er a\u00f0 n\u00fdta l\u00edp\u00f3s\u00f3m til a\u00f0 auka st\u00f6\u00f0ugleika l\u00edfvirkra efna, en einnig er nau\u00f0synlegt a\u00f0 auka st\u00f6\u00f0ugleika l\u00edp\u00f3s\u00f3ma. \u00cd \u00feessari ranns\u00f3kn voru br\u00fanu st\u00f3r\u00fe\u00f6rungarnir Laminaria digitata, Alaria esculenta, rau\u00f0i st\u00f3r\u00fe\u00f6rungurinn Palmaria palmata og hinn gr\u00e6ni Ulva lactuca nota\u00f0ir til a\u00f0 \u00fatb\u00faa \u00fatdr\u00e6tti me\u00f0 PEF. Lei\u00f0ni og s\u00fdrustig voru m\u00e6ld og jafnframt var magn fj\u00f6lfen\u00f3la og kolvetna greint. Andoxun var metin me\u00f0 FRAP- og DPPH-m\u00e6lingum. Tegund \u00fe\u00f6runga haf\u00f0i \u00e1hrif \u00e1 skilvirkni \u00fatdr\u00e1tta me\u00f0 PEF. H\u00e6rri gildi b\u00e6\u00f0i fj\u00f6lfen\u00f3la og kolvetna m\u00e6ldust \u00ed PEF \u00fatdr\u00e6tti fr\u00e1 Ulva lactuca. \u00cd Alaria esculenta voru kolvetnisheimtur helmingi h\u00e6rri \u00ed PEF vatns\u00fatdr\u00e6tti mi\u00f0a\u00f0 vi\u00f0 \u00fatdr\u00e1tt \u00fear sem PEF var ekki framkv\u00e6mt. Vatn var betri leysir en 15% etan\u00f3l fyrir PEF-\u00fatdr\u00e1tt. Til vi\u00f0b\u00f3tar voru \u00fatb\u00fain l\u00edp\u00f3som af \u00feremur mismunandi st\u00e6r\u00f0um (\u00feverm\u00e1l 0.09, 0.40 og 2.7 \u03bcm). L\u00edp\u00f3s\u00f3min voru h\u00fa\u00f0u\u00f0 me\u00f0 kaldsj\u00e1varfiskigelat\u00edni. Til a\u00f0 meta st\u00f6\u00f0ugleika l\u00edp\u00f3soma voru lausnirnar \u00feykktar \u00ed gegnum osm\u00f3su. Fylgst var me\u00f0 breytingu \u00e1 \u00feyngd lausna og st\u00e6r\u00f0 l\u00edp\u00f3s\u00f3ma. H\u00fa\u00f0un me\u00f0 kaldsj\u00e1varfiskigelat\u00edni j\u00f3k st\u00f6\u00f0ugleika \u00feeirra. \u00deessi ranns\u00f3kn s\u00fdndi fram \u00e1 h\u00e6gt er a\u00f0 h\u00fa\u00f0a l\u00edp\u00f3s\u00f3m af \u00fdmsum st\u00e6r\u00f0um me\u00f0 kaldsj\u00e1varfiskigelat\u00edni. \u00dear a\u00f0 auki er PEF raunh\u00e6f a\u00f0fer\u00f0 til a\u00f0 draga \u00fat l\u00edfvirk efni \u00far st\u00f3r\u00fe\u00f6rungum \u00e1n \u00feess a\u00f0 nota h\u00e1an hita e\u00f0a l\u00edfr\u00e6na leysa.\u00a0<\/strong><\/p>\n

English abstract<\/strong><\/p>\n

Macroalgae are an underutilised source of bioactive compounds such as polyphenols, carbohydrates, proteins, and carotenoids, for the food, cosmetics, and pharmaceutical industries. Furthermore, these industries are searching for high-quality bioactive compounds that are produced with green, organic, solvent-free methods. Pulsed electric field (PEF)-assisted extraction is a promising non-thermal, low-energy extraction method, but there are limited studies on macroalgae. Moreover, these bioactive compounds can be incorporated in lipid delivery systems, such as liposomes, to increase their stability. PEF has been used to produce crude extracts from the brown macroalgae Laminaria digitata and Alaria esculenta, the red macroalgae Palmaria palmata, and the green macroalgae Ulva lactuca. Their conductivity, polyphenol, and carbohydrate content were analysed alongside ferric-reducing antioxidant (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activity. The efficiency of the PEF treatment was compound and species specific. In Ulva lactuca it allowed for higher extraction yields of both polyphenols and carbohydrates, and in Alaria esculenta it gave twice as high extraction of carbohydrates compared with gentle heating at 55\u00b0C, whereas there was no difference in polyphenol extraction. Water, compared with 15% ethanol, was a better solvent for PEF treatment and PEF had a shorter extraction time. In addition, liposomes of three different sizes (0.09, 0.40, and 2.7 \u03bcm) were produced with either high-pressure homogenisation or extrusion through a polycarbonate membrane. Liposomes were then coated with cold-water fish skin gelatin by layer-by-layer deposition. Their stability was evaluated with osmotic dehydration, while monitoring their relative weight and size. Coating the liposomes with gelatin increased their physical stability. The results show that cold-water fish skin gelatin is a viable option for coating liposomes of a wide range in size. Furthermore, PEF-assisted extraction can be used for the extraction of valuable compounds from macroalgae without high heat or organic solvents.<\/p>\n

Um doktorsefni\u00f0<\/strong><\/p>\n

Ragnhildur Einarsd\u00f3ttir er f\u00e6dd \u00e1ri\u00f0 1982 \u00ed Reykjav\u00edk. H\u00fan lauk st\u00fadentspr\u00f3fi af n\u00e1tt\u00farufr\u00e6\u00f0ibraut I fr\u00e1 Menntask\u00f3lanum \u00ed Reykjav\u00edk \u00e1ri\u00f0 2002, BS-pr\u00f3fi \u00ed matv\u00e6lafr\u00e6\u00f0i fr\u00e1 H\u00e1sk\u00f3la \u00cdslands \u00e1ri\u00f0 2006 og meistarapr\u00f3fi \u00ed matv\u00e6lafr\u00e6\u00f0i fr\u00e1 sama sk\u00f3la \u00e1ri\u00f0 2010. Ragnhildur starfa\u00f0i sem stundakennari hj\u00e1 H\u00e1sk\u00f3la \u00cdslands og hj\u00e1 TARAMAR ehf. samhli\u00f0a doktorsn\u00e1mi s\u00ednu. Foreldrar hennar eru Einar Hrafnsson og Mar\u00eda J\u00f3natansd\u00f3ttir. Samb\u00fdlisma\u00f0ur hennar er Kevin Gillies.<\/p>\n<\/div><\/div>","protected":false},"featured_media":5598,"template":"","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"_phd_date_start":"2022-12-16T13:00:00+00:00","_phd_date_end":"2022-12-16T16:00:00+00:00","_phd_location":"A\u00f0albygging H\u00e1t\u00ed\u00f0asalur","_phd_admission":"A\u00f0gangur \u00f3keypis","_phd_thesis_title":"\u00datdr\u00e1ttur \u00e1 l\u00edfvirkum efnum \u00far st\u00f3r\u00fe\u00f6rungum me\u00f0 p\u00falsu\u00f0u rafsvi\u00f0i. \u00c1hrif st\u00e6r\u00f0ar l\u00edp\u00f3s\u00f3ma \u00e1 h\u00fa\u00f0un me\u00f0 kaldsj\u00e1varfiskigelat\u00edni. Novel extraction of bioactive compounds from macroalgae with pulsed electric field. The influence on liposomal dispersions of particle size and electrostatic deposition of cold water fish skin gelatin","_phd_source_url":"https:\/\/gamli.hi.is\/vidburdir\/doktorsvorn_i_matvaelafraedi_ragnhildur_einarsdottir","_phd_source_node_id":"391575","_phd_source_type":"vidburdir","_phd_member_id":853,"footnotes":""},"phd_school":[60,72],"phd_discipline":[74],"class_list":["post-6317","phd_defence","type-phd_defence","status-publish","has-post-thumbnail","hentry","phd_school-heilbrigdisvisindasvid","phd_school-matvaela-og-naeringafraedideild","phd_discipline-phd-i-matvaelafraedi"],"_links":{"self":[{"href":"https:\/\/phd.hi.is\/en\/wp-json\/wp\/v2\/phd_defence\/6317","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/phd.hi.is\/en\/wp-json\/wp\/v2\/phd_defence"}],"about":[{"href":"https:\/\/phd.hi.is\/en\/wp-json\/wp\/v2\/types\/phd_defence"}],"version-history":[{"count":0,"href":"https:\/\/phd.hi.is\/en\/wp-json\/wp\/v2\/phd_defence\/6317\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/phd.hi.is\/en\/wp-json\/wp\/v2\/media\/5598"}],"wp:attachment":[{"href":"https:\/\/phd.hi.is\/en\/wp-json\/wp\/v2\/media?parent=6317"}],"wp:term":[{"taxonomy":"phd_school","embeddable":true,"href":"https:\/\/phd.hi.is\/en\/wp-json\/wp\/v2\/phd_school?post=6317"},{"taxonomy":"phd_discipline","embeddable":true,"href":"https:\/\/phd.hi.is\/en\/wp-json\/wp\/v2\/phd_discipline?post=6317"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}