Showing papers by "University of Iceland published in 2005"

Classification of hyperspectral data from urban areas based on extended morphological profiles

Abstract: Classification of hyperspectral data with high spatial resolution from urban areas is investigated. A method based on mathematical morphology for preprocessing of the hyperspectral data is proposed. In this approach, opening and closing morphological transforms are used in order to isolate bright (opening) and dark (closing) structures in images, where bright/dark means brighter/darker than the surrounding features in the images. A morphological profile is constructed based on the repeated use of openings and closings with a structuring element of increasing size, starting with one original image. In order to apply the morphological approach to hyperspectral data, principal components of the hyperspectral imagery are computed. The most significant principal components are used as base images for an extended morphological profile, i.e., a profile based on more than one original image. In experiments, two hyperspectral urban datasets are classified. The proposed method is used as a preprocessing method for a neural network classifier and compared to more conventional classification methods with different types of statistical computations and feature extraction.

Cyclodextrins in drug delivery

Abstract: Cyclodextrins are a family of cyclic oligosaccharides with a hydrophilic outer surface and a lipophilic central cavity. Cyclodextrin molecules are relatively large with a number of hydrogen donors and acceptors and, thus, in general they do not permeate lipophilic membranes. In the pharmaceutical industry cyclodextrins have mainly been used as complexing agents to increase aqueous solubility of poorly soluble drugs, and to increase their bioavailability and stability. Studies in both humans and animals have shown that cyclodextrins can be used to improve drug delivery from almost any type of drug formulation. However, the addition of cyclodextrins to existing formulations without further optimisation will seldom result in acceptable outcome. Currently there are approximately 30 different pharmaceutical products worldwide containing drug/cyclodextrin complexes on the market.

Search biases in constrained evolutionary optimization

Abstract: A common approach to constraint handling in evolutionary optimization is to apply a penalty function to bias the search toward a feasible solution. It has been proposed that the subjective setting of various penalty parameters can be avoided using a multiobjective formulation. This paper analyzes and explains in depth why and when the multiobjective approach to constraint handling is expected to work or fail. Furthermore, an improved evolutionary algorithm based on evolution strategies and differential variation is proposed. Extensive experimental studies have been carried out. Our results reveal that the unbiased multiobjective approach to constraint handling may not be as effective as one may have assumed.

National character does not reflect mean personality trait levels in 49 cultures

Abstract: Most people hold beliefs about personality characteristics typical of members of their own and others' cultures. These perceptions of national character may be generalizations from personal experience, stereotypes with a "kernel of truth," or inaccurate stereotypes. We obtained national character ratings of 3989 people from 49 cultures and compared them with the average personality scores of culture members assessed by observer ratings and self-reports. National character ratings were reliable but did not converge with assessed traits. Perceptions of national character thus appear to be unfounded stereotypes that may serve the function of maintaining a national identity.

GRIP deuterium excess reveals rapid and orbital-scale changes in Greenland moisture origin.

Abstract: The Northern Hemisphere hydrological cycle is a key factor coupling ice sheets, ocean circulation, and polar amplification of climate change. Here we present a Northern Hemisphere deuterium excess profile covering one climatic cycle, constructed with the use of δ 18 O and δD Greenland Ice Core Project (GRIP) records. Past changes in Greenland source and site temperatures are quantified with precipitation seasonality taken into account. The imprint of obliquity is evidenced in the site-to-source temperature gradient at orbital scale. At the millennial time scale, GRIP source temperature changes reflect southward shifts of the geographical locations of moisture sources during cold events, and these rapid shifts are associated with large-scale changes in atmospheric circulation.

An Icelandic example of the impact of population structure on association studies

Abstract: The impact of population structure on association studies undertaken to identify genetic variants underlying common human diseases is an issue of growing interest1,2,3,4. Spurious associations of alleles with disease phenotypes may be obtained or true associations overlooked when allele frequencies differ notably among subpopulations that are not represented equally among cases and controls. Population structure influences even carefully designed studies and can affect the validity of association results1,2. Most study designs address this problem by sampling cases and controls from groups that share the same nationality or self-reported ethnic background, with the implicit assumption that no substructure exists within such groups. We examined population structure in the Icelandic gene pool using extensive genealogical and genetic data. Our results indicate that sampling strategies need to take account of substructure even in a relatively homogenous5 genetic isolate6. This will probably be even more important in larger populations.

Myoepithelial cells: their origin and function in breast morphogenesis and neoplasia.

Abstract: The human breast epithelium is a branching ductal system composed of an inner layer of polarized luminal epithelial cells and an outer layer of myoepithelial cells that terminate in distally located terminal duct lobular units (TDLUs). While the luminal epithelial cell has received the most attention as the functionally active milk-producing cell and as the most likely target cell for carcinogenesis, attention on myoepithelial cells has begun to evolve with the recognition that these cells play an active part in branching morphogenesis and tumor suppression. A major question that has been the subject of investigation pertains to how the luminal epithelial and myoepithelial lineages are related and precisely how they arise from a common putative stem cell population within the breast. Equally important is the question of how heterotypic signaling occurs between luminal epithelial and surrounding myoepithelial cells in normal breast morphogenesis and neoplasia. In this review we discuss data from our laboratories and from others regarding the cellular origin of human myoepithelial cells, their function in maintaining tissue polarity in the normal breast, and their role during neoplasia.

Persistent organochlorines, sedentary occupation, obesity and human male subfertility

Abstract: Background Studies have suggested that the quality of human semen has been declining over recent decades, presumably because of lifestyle or environmental factors. Methods Polychlorinated biphenyls and organochlorine pesticides were analysed in the plasma of 25 men with poor semen quality, 20 men with normal semen quality and idiopathic subfertility and 27 men with normal semen quality and female factor subfertility. Samples of seminal fluid were also analysed to assess the relationship between the levels in blood and semen. Results The results indicate no difference in the levels of organochlorines between the groups. The levels of organochlorines in seminal fluid were proportional to the levels in plasma, but approximately 40 times lower. Men with poor semen quality were three times more likely to be obese than men with normal semen quality. There was also a significant negative correlation between semen quality parameters and body mass index among men with normal semen quality. The prevalence of sedentary work was lowest among men with the best semen quality. Conclusions Poor semen quality was found to be associated with sedentary work and obesity but not with plasma levels of persistent organochlorines. More research is needed to assess whether sedentary lifestyle and obesity are causal factors in the decline of semen quality.

CFH Y402H Confers Similar Risk of Soft Drusen and Both Forms of Advanced AMD

Abstract: Background Age-related macular degeneration (AMD) is the most common cause of irreversible visual impairment in the developed world. The two forms of advanced AMD, geographic atrophy and neovascular AMD, represent different pathological processes in the macula that lead to loss of central vision. Soft drusen, characterized by deposits in the macula without visual loss, are considered to be a precursor of advanced AMD. Recently, it has been proposed that a common missense variant, Y402H, in the Complement Factor H (CFH) gene increases the risk for advanced AMD. However, its impact on soft drusen, GA, or neovascular AMD—or the relationship between them—is unclear.

Land degradation control and its global environmental benefits

Abstract: Acknowledged by world leaders as a global problem, land degradation has been taken seriously in three ways: its extent and the proportion of the global population affected; international environmental policy responses; and its inter-relation with other global environmental issues such as biodiversity. Messages about land degradation have, however, suffered from abuses, which have rendered appropriate policy responses ineffective. For control to be effective, the paper argues that the synergies between land degradation and the two other main global environmental change components (biodiversity and climate change) should be more fully exploited. A focus on the interlinkages, of which there are six possible permutations, is fully supported by empirical findings that suggest that land degradation control would not only technically be better served by addressing aspects of biodiversity and climate change but also that international financing mechanisms and the major donors would find this more acceptable. The DPSIR (Driving Force, Pressure, State, Impacts, Response) conceptual framework model is used to illustrate how land degradation control could be more effective, tackling not only the drivers of change but also major developmental issues such as poverty and food insecurity. Copyright © 2005 John Wiley & Sons, Ltd.

Profile and competences for the European dentist.

Abstract: This paper presents the profile and competences for the European Dentist as approved by the General Assembly of the Association for Dental Education in Europe at its annual meeting held in Cardiff in September 2004. A task-force drafted the document, which was then sent to all European Dental Schools. Reactions received were used to amend the document. European dental schools are expected to adhere to the profile and the 17 major competences but the supporting competences may vary in detail between schools. The document will be reviewed in 5 years time. This paper will be disseminated to ministries of health, national dental associations and dental specialty associations or societies in Europe and these organisations will be asked to offer their comments. This information will be used in the reviewing process to be started in 2007. It is hoped that the availability of this document will assist dental schools in Europe to further harmonize and improve the quality of their curricula.

Ion-assisted physical vapor deposition for enhanced film properties on nonflat surfaces

Abstract: We have synthesized Ta thin films on Si substrates placed along a wall of a 2-cm-deep and 1-cm-wide trench, using both a mostly neutral Ta flux by conventional dc magnetron sputtering (dcMS) and a mostly ionized Ta flux by high-power pulsed magnetron sputtering (HPPMS). Structure of the grown films was evaluated by scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The Ta thin film grown by HPPMS has a smooth surface and a dense crystalline structure with grains oriented perpendicular to the substrate surface, whereas the film grown by dcMS exhibits a rough surface, pores between the grains, and an inclined columnar structure. The improved homogeneity achieved by HPPMS is a direct consequence of the high ion fraction of sputtered species.

Risk Factors for Acute Cellulitis of the Lower Limb: A Prospective Case-Control Study

Abstract: Background Acute bacterial cellulitis is a potentially serious infection that commonly recurs. The identification of preventable risk factors could reduce infection-related morbidity and cost and improve patient management. The aim of this study was to identify the risk factors associated with lower-limb cellulitis, including both analysis of risk factors associated with cellulitis in either limb and risk factors in a single limb associated with cellulitis in the same limb. We placed particular emphasis on dermatophytic infections of the foot and bacterial infection and colonization of the toe webs. Methods We conducted a prospective case-control study of 100 subjects with cellulitis and 200 control subjects, matched for age and sex, who were admitted to a university hospital during the period October 2000-February 2004. Data were obtained with a questionnaire and from examination of lower limbs and microbiological analyses of samples from the feet. Results The median age of the participants was 66.5 years (interquartile range, 48.8-77.0). The following risk factors were strongly and independently associated with cellulitis: previous history of cellulitis (OR, 31.04; 95% CI, 4.15-232.20), the presence of Staphylococcus aureus and/or beta -hemolytic streptococci in the toe webs (OR, 28.97; 95% CI, 5.47-153.48), presence of leg erosions or ulcers (OR, 11.80; 95% CI, 2.47-56.33), and prior saphenectomy (OR, 8.49; 95% CI, 1.62-44.52). Tinea pedis interdigitalis was associated with cellulitis only when toe web bacteria were excluded from the analysis (OR, 3.86; 95% CI, 1.32-11.27). Conclusions Risk factors for acute bacterial cellulitis in hospitalized patients include predisposing factors and the presence of sites of pathogen entry on legs and toe webs. These findings indicate that improved awareness and management of toe web intertrigo, which may harbor bacterial pathogens, and other skin lesions might reduce the incidence of cellulitis.

Postglacial eruptive history of the Western Volcanic Zone, Iceland

Abstract: New field observations, age constraints, and extensive chemical analyses define the complete postglacial eruptive history of the 170-km-long Western Volcanic Zone (WVZ) of Iceland, the ultraslow-spreading western boundary of the south Iceland microplate. We have identified 44 separate eruptive units, 10 of which are small-volume eruptions associated with the flanking Grimsnes system. Overall chemical variations are consistent with very simplified models of melting of a source approximating primitive mantle composition. The 17 eruptions in the first 3000 years of postglacial time account for about 64% of the total postglacial production and are incompatible-element depleted compared to younger units, consistent with enhanced melting as a consequence of rebound immediately following deglaciation. Steadily declining eruption rates for the last 9000 years also correlate with changes in average incompatible element ratios that appear to reflect continued decline in melting extents to the present day. This result is not restricted to the WVZ, however, and may herald a decline in melting throughout all of western Iceland during later postglacial time. Lavas from the northern part of the WVZ are depleted in incompatible elements relative to those farther south at all times, indicating either a long-wavelength gradient in mantle source composition or variations in the melting process along axis. We find no evidence in the postglacial volcanic record for current failure of the WVZ, despite evidence for continued propagation of the eastern margin of the microplate. The dominance of lava shields in the eruptive history of the WVZ contrasts with the higher number of fissure eruptions in other Icelandic volcanic zones. WVZ shields represent long-duration, low-effusion rate eruptions fed by recharge magma arising out of the mantle. Average effusion rate is the key variable distinguishing shield and fissure eruptions, both within the WVZ and between different volcanic zones. High effusion rate, large-volume eruptions require the presence of large crustal magma reservoirs, which have been rare or absent in the WVZ throughout postglacial time.

Respiratory syncytial virus and other respiratory viruses during the first 3 months of life promote a local TH2-like response

Abstract: Background Respiratory syncytial virus (RSV) infections during infancy are considered to be a risk factor for developing asthma and possibly allergic sensitization. Objective The aim of this study was to investigate the cytokines, chemokines, and eosinophil cationic protein in the nasopharyngeal secretions of infants ≤7 months of age with RSV infections or other respiratory viral infections and healthy infants as controls. Groups were also analyzed according to age, ≤3 months and >3 months, and the levels were compared within and between groups. Results Thirty-nine infants with RSV, 9 with influenza or parainfluenza virus infections and 50 controls with no history of infections, were enrolled in the study. The RSV-infected infants had significantly higher levels of IL-4; macrophage inflammatory protein 1β, a chemoattractant for T cells; and eosinophil cationic protein in nasopharyngeal secretions compared with the control group. The levels of the T h 2 cytokine IL-4 were significantly higher in RSV-infected infants ≤3 months of age compared with RSV-infected infants >3 months of age. In infants ≤3 months of age, infections with influenza or parainfluenza virus caused T h 2-like responses similar to those produced by RSV. Conclusion Infections with RSV as well as with influenza and parainfluenza virus during early infancy preferentially promote a T h 2-like response in the nose with local production of IL-4, IL-5, and macrophage inflammatory protein 1β and infiltration and activation of eosinophils.

Evidence for solar forcing of sea-surface temperature on the North Icelandic Shelf during the late Holocene

Abstract: Diatom proxies from the modern position of the oceanographic Polar Front north of Iceland record variability in sea-surface temperatures (SSTs) during the past 2 k.y. The sedimentary record is dated with tephrochronology, alleviating marine 14C reservoir age uncertainties. Comparison of changes in SSTs on the North Icelandic Shelf with variations in the atmospheric circulation above Greenland, North American Atlantic coastal SSTs, and mean temperature anomalies for the Northern Hemisphere suggests synchronous North Atlantic–wide fluctuations, which would seem to imply a common forcing factor. A positive and significant correlation between our SST record from the North Icelandic Shelf and reconstructed solar irradiance, together with modeling results, supports the hypothesis that solar forcing is an important constituent of natural climate variability in the northern North Atlantic region.

Property Rights in Fisheries: Iceland’s Experience with ITQs

Abstract: The fundamental problem of economic inefficiency in fisheries, the so-called common property problem, may be seen to be caused by inadequate or lacking property rights in the underlying natural resources. The introduction of Individual Transferable Quotas (ITQs) into fisheries represents an attempt to correct this failure. ITQs, however, are not property rights in the relevant natural resources, i.e. the fish stocks and their habitat. They are merely harvesting rights and thus far from ideal as property rights. Nevertheless, ITQs have been introduced in numerous fisheries around the world, apparently with generally, even consistently, good economic results. This paper outlines the basic theory of property rights and the strengths and weaknesses of ITQs as property rights in fisheries. The paper goes on to discuss the Icelandic ITQ system and compares its property rights value with that of the New Zealand ITQ system and the Norwegian IQ system. Finally, the paper reviews some measures of the economic outcomes of the ITQ system in Iceland.

Assessing and Managing Rapid Credit Growth and the Role of Supervisory and Prudential Policies

Abstract: This paper reviews trends in bank lending to the private sector, with a particular focus on Central and Eastern European countries, and finds that rapid growth of private sector credit continues to be a key challenge for most of these countries. The paper discusses possible implications for economic and financial stability and the policy options available to counter and reduce these risks. It argues that the authorities will need to focus on the implications for both the macro economy and the financial system and, depending on their assessment, may need a comprehensive policy response comprising a mix of macro and prudential policies. In particular where there are limitations to the effective use of monetary and fiscal measures, supervisory and prudential policy responses will have a key role in addressing financial stability concerns.

Breast and ovarian cancer risks to carriers of the BRCA1 5382insC and 185delAG and BRCA2 6174delT mutations: a combined analysis of 22 population based studies

Abstract: A recent report estimated the breast cancer risks in carriers of the three Ashkenazi founder mutations to be higher than previously published estimates derived from population based studies. In an attempt to confirm this, the breast and ovarian cancer risks associated with the three Ashkenazi founder mutations were estimated using families included in a previous meta-analysis of populatrion based studies. The estimated breast cancer risks for each of the founder BRCA1 and BRCA2 mutations were similar to the corresponding estimates based on all BRCA1 or BRCA2 mutations in the meta-analysis. These estimates appear to be consistent with the observed prevalence of the mutations in the Ashkenazi Jewish population.

Isolation and identification of antimicrobial components from the epidermal mucus of Atlantic cod (Gadus morhua)

Abstract: The epidermal mucus of fish species has been found to contain antimicrobial proteins and peptides, which is of interest in regard to fish immunity. An acidic extract from the epidermal mucus of the Atlantic cod (Gadus morhua) was found to exhibit antimicrobial activity against Bacillus megaterium, Escherichia coli and Candida albicans. This activity varied significantly when salt was added to the antimicrobial assay, and was eliminated by pepsin digestion. No lysozyme activity was detected in the extract. By using weak cationic exchange chromatography together with reversed-phase chromatography, and monitoring the antimicrobial activity, we have isolated four cationic proteins from the mucus extract. Using N-terminal and C-terminal amino acid sequence analysis, together with MS, the antimicrobial proteins were identified as histone H2B (13 565 Da), ribosomal protein L40 (6397 Da), ribosomal protein L36A (12 340 Da) and ribosomal protein L35 (14 215 Da). The broad spectra of antimicrobial activities in the cod mucus and the characterization of four antimicrobial polypeptides suggest that mucus compounds contribute to the innate host defence of cod.

GPs’ reasons for “non-pharmacological” prescribing of antibiotics A phenomenological study

Abstract: Objective To study the reasons cited by Icelandic general practitioners for their “non-pharmacological” prescribing of antibiotics. Design A qualitative interview study with research dialogues guided by the Vancouver School of doing phenomenology. Setting General practice. Participants A total of 16 general practitioners: 11 in the maximum variety sample and 5 in the theoretical sample. Results The most important reasons for prescribing antibiotics in situations with low pharmacological indications (non-pharmacological prescribing) were an unstable doctor–patient relationship due to lack of continuity of care, patient pressure in a stress-loaded society, the doctor's personal characteristics, particularly zeal and readiness to serve, and, finally, the insecurity and uncertainty of the doctor who falls back on the prescription as a coping strategy in a difficult situation. Conclusion The causes of non-pharmacological prescribing of antibiotics are highly varied, and relational factors in the interplay betw...

Rethinking Late Weichselian ice-sheet dynamics in coastal NW Svalbard

Abstract: New marine geological evidence provides a better understanding of ice-sheet dynamics along the western margin of the last Svalbard/Barents Sea Ice Sheet. A suite of glacial sediments in the Kongsfjordrenna cross-shelf trough can be traced southwards to the shelf west of Prins Karls Forland. A prominent moraine system on the shelf shows minimum Late Weichselian ice extent, indicating that glacial ice also covered the coastal lowlands of northwest Svalbard. Our results suggest that the cross-shelf trough was filled by a fast-flowing ice stream, with sharp boundaries to dynamically less active ice on the adjacent shelves and strandflats. The latter glacial mode favoured the preservation of older geological records adjacent to the main pathway of the Kongsfjorden glacial system. We suggest that the same model may apply to the Late Weichselian glacier drainage along other fjords of northwest Svalbard, as well as the western margin of the Barents Ice Sheet. Such differences in glacier regime may explain the apparent contradictions between the marine and land geological record, and may also serve as a model for glaciation dynamics in other fjord regions.

Caring for a child with cancer: a longitudinal perspective.

Abstract: Aims. This paper reports a study to evaluate caregiving demands among mothers and fathers of children with cancer, parents’ well-being, and how the parents perceive the health status of their child over a period of 18 months. Background. Cancer among children has psychological impact on all family members. Most previous research has focused on distress, coping patterns and social support, and less is known about how parents are dealing with the illness experience over time. No study was found that evaluated caregiving on a daily basis, or the impact of the cancer on wellbeing and perceptions of health within families. Methods. Data were collected between 1999 and 2001. Parents of 26 Icelandic children under 18 years with cancer completed questionnaires about caregiving activities, general wellbeing and health perceptions. Descriptive statistics and Repeated Analyses of Variance were conducted at baseline, 12 and 18 months. Results. The most time-consuming and difficult caregiving activities for both mothers and fathers were giving emotional support to the child with cancer, and to other children in the family. Mothers also found it difficult and time-consuming to manage behavioural problems and to structure and plan activities for the family. Fathers found it difficult to manage work and organize care for the child at the same time, and to give their partner emotional support. When evaluated over time, mothers’ caregiving demands differed statistically significantly from fathers’, and fathers’ caregiving demands and health perceptions changed statistically significantly over the 18 months of the study. Conclusion. These findings underline the long-term impact of children's cancer on their families. Interventions focusing on emotional support, parents’ wellbeing, and how families perceive the health of their child with cancer might benefit the family as a whole.

Prevalence of chronic kidney disease based on estimated glomerular filtration rate and proteinuria in Icelandic adults

Abstract: Background. The purpose of this study was to compare three different equations to calculate estimated glomerular filtration rate (eGFR) based on serum creatinine (SCr) and to estimate the prevalence of chronic kidney disease (CKD) in the Icelandic population. Methods. This was a cross-sectional study using data from the Reykjavik Heart Study. GFR was estimated with three equations: Equation I was based on 1/SCr; Equation II based on the Cockcroft-Gault equation; and Equation III was the modified MDRD equation. The eGFR calculated with Equation III and proteinuria were used to estimate the prevalence of CKD. The prevalence was age-standardized to the truncated world population. We used � -square and ANCOVA to compare the group with low eGFR to age-matched controls. Results. The subjects consisted of 9229 males and 10 027 females, aged 33–85 years. The equations performed very differently. Equation I showed women with higher eGFR than men and little change with age. Equation II showed men with higher eGFR than women and marked decline in eGFR with age. Equation III was similar to Equation II but the decline in eGFR with age was not as great. Regardless of the equation used, most subjects (63.7–80.7%) had an eGFR in the range of 60–89 ml/min/1.73 m 2 . Using Equation III, age-standardized prevalence of low eGFR for the population aged 35–80þ years was estimated to be 4.7 and 11.6% for men and women, respectively. The proportion of subjects with eGFR <60 ml/min/1.73 m 2 increased with advancing age. An additional 2.39% of men and 0.89% of women had proteinuria. The prevalence of renal and cardiovascular risk factors including proteinuria, hypertension, lipid abnormalities and markers of inflammation was higher among those with low eGFR than age-matched controls. Conclusions. GFR estimates and the prevalence of CKD are dependent on the equation used to calculate eGFR. Unexpectedly, a low proportion of the Icelandic population had normal kidney function according to the eGFR regardless of the equation used. These equations may not be useful in epidemiological research.

Neisseria gonorrhoeae downregulates expression of the human antimicrobial peptide LL‐37

Abstract: Neisseria gonorrhoeae is a human pathogen causing the sexually transmitted disease gonorrhoeae. The bacteria preferentially attach to and invade epithelial cells of the genital tract. As these cells previously have been shown to express the human cathelicidin LL-37, we wanted to investigate the role of LL-37 during N. gonorrhoeae infection. The cervical epithelial cell line ME180 was utilized and the expression of LL-37 was confirmed on both peptide and transcriptional levels. Moreover, LL-37 exhibited potent in vitro activity against N. gonorrhoeae. Interestingly, the transcript and peptide levels of LL-37 were downregulated during infection, according to quantitative real-time polymerase chain reaction (PCR) and immunocyto-chemistry. The downregulation was most prominent with pathogenic strains of Neisseria, while non-pathogenic strains such as Neisseria lactamica and Escherichia coli only exhibited moderate effects. Heat-killed N. gonorrhoeae had no impact on the downregulation, emphasizing the importance of live bacteria. The results in this study suggest that pathogenic Neisseria may gain a survival advantage in the female genital tract by downregulating LL-37 expression.

Characterization of Volatile Compounds in Chilled Cod (Gadus morhua) fillets by gas chromatography and detection of quality indicators by an electronic nose

Abstract: Volatile compounds in cod fillets packed in Styrofoam boxes were analyzed during chilled storage (0.5 degrees C) by gas chromatography (GC)-mass spectrometry and GC-olfactometry to screen potential quality indicators present in concentrations high enough for detection by an electronic nose. Photobacterium phosphoreum dominated the spoilage bacteria on day 12 when the fillets were rejected by sensory analysis. Ketones, mainly 3-hydroxy-2-butanone, were detected in the highest level (33%) at sensory rejection, followed by amines (TMA) (29%), alcohols (15%), acids (4%), aldehydes (3%), and a low level of esters (<1%). The electronic nose's CO sensor showed an increasing response with storage time coinciding with the production of ethanol and 2-methyl-1-propanol that were produced early in the storage, followed by the production of 3-methyl-1-butanol, 3-methyl-butanal, 2,3-butandiol, and ethyl acetate. Lipid-derived aldehydes, like hexanal and decanal, were detected in similar levels throughout the storage time and contributed to the overall sweet odors of cod fillets in combination with other carbonyls (3-hydroxy-2-butanone, acetaldehyde, 2-butanone, 3-pentanone, and 6-methyl-5-heptene-2-one).