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Feed comprises the biggest cost in intensive fish farming and the quality of feed is therefore important. A vast body of research has been carried out in order to investigate nutritional quality of alternative ingredients. Effects of ingredients on physical quality are seldom included in these investigations. Physical quality of feed varies with ingredient composition and processing condition and may interfere with feed intake, nutrient digestibility and therefore growth performance of the fish. In this review, physical quality of extruded, high energy feed, and how ingredient composition and processing conditions affect the quality will be addressed. Various pellet properties will be discussed and methods used to evaluate physical quality will be reviewed. © 2012 Blackwell Publishing Ltd.

Rotabakk B.T.,Nofima AS
European Food Research and Technology | Year: 2013

The solubility of carbon dioxide (CO2) in a seafood model product with various amounts of salmon oil was investigated. Differential scanning calorimetry analysis of the salmon oil gave an onset temperature for crystallization at -14.75 ± 0.74 °C, showing that the oil was in liquid state in the temperature range used in this experiment (1-8 °C). Solubility of CO2 in salmon oil in liquid state was similar to water, with the same temperature dependency as water. Increased storage temperature decreased the amount of dissolved CO2 and increased the headspace CO2 and headspace gas volume. Headspace gas composition at equilibrium was linearly (R 2 = 0.979) related to the composition of the packaging gas, while increasing CO2 in the packaging gas increased the headspace gas volume and the amount of dissolved CO2 in the product. When designing modified gas-packaging regimes for products with marine fat, sum of fat and water can be used to estimate the amount of dissolved CO2 in the product. © 2013 Springer-Verlag Berlin Heidelberg.

Kause A.,Mtt Agrifood Research Finland | Odegard J.,Nofima AS
Frontiers in Genetics | Year: 2012

Tolerance to infections is defined as the ability of a host to limit the impact of a given pathogen burden on host performance. Uncoupling resistance and tolerance is a challenge, and there is a need to be able to separate them using specific trait recording or statistical methods. We present three statistical methods that can be used to investigate genetics of tolerance-related traits. Firstly, using random regressions, tolerance can be analyzed as a reaction norm slope in which host performance (y-axis) is regressed against an increasing pathogen burden (x-axis). Genetic variance in tolerance slopes is the genetic variance for tolerance. Variation in tolerance can induce genotype re-ranking and changes in genetic and phenotypic variation in host performance along the pathogen burden trajectory, contributing to environment-dependent genetic responses to selection. Such genotype-by-environment interactions can be quantified by combining random regressions and covariance functions. To apply random regressions, pathogen burden of individuals needs to be recorded. Secondly, when pathogen burden is not recorded, the cure model for time-until-death data allows separating two traits, susceptibility and endurance. Susceptibility is whether or not an individual was susceptible to an infection, whereas endurance denotes how long time it took until the infection killed a susceptible animal (influenced by tolerance). Thirdly, the normal mixture model can be used to classify continuously distributed host performance, such as growth rate, into different sub-classes (e.g., non-infected and infected), which allows estimation of host performance reduction specific to infected individuals. Moreover, genetics of host performance can be analyzed separately in healthy and affected animals, even in the absence of pathogen burden and survival data. These methods provide novel tools to increase our understanding on the impact of parasites, pathogens, and production diseases on host traits. © 2012 Kause and Ødegård.

Vazquez-Sanchez D.,CSIC - Institute of Marine Research | Habimana O.,University College Dublin | Holck A.,Nofima AS
Current Microbiology | Year: 2013

Staphylococcus aureus is a pathogenic bacterium capable of developing biofilms on food-processing surfaces, a pathway leading to cross contamination of foods. The purpose of this study was to investigate the influence of environmental stress factors found during seafood production on the adhesion and biofilm-forming properties of S. aureus. Adhesion and biofilm assays were performed on 26 S. aureus isolated from seafood and two S. aureus reference strains (ATCC 6538 and ATCC 43300). Cell surface properties were evaluated by affinity measurements to solvents in a partitioning test, while adhesion and biofilm assays were performed in polystyrene microplates under different stress conditions of temperature, osmolarity, and nutrient content. The expression of genes implicated in the regulation of biofilm formation (icaA, rbf and σ B ) was analyzed by reverse transcription and quantitative real time PCR. In general, S. aureus isolates showed moderate hydrophobic properties and a marked Lewis-base character. Initial adhesion to polystyrene was positively correlated with the ionic strength of the growth medium. Most of the strains had a higher biofilm production at 37 °C than at 25 °C, promoted by the addition of glucose, whereas NaCl and MgCl2 had a lower impact markedly affected by incubation temperatures. Principal Component Analysis revealed a considerable variability in adhesion and biofilm-forming properties between S. aureus isolates. Transcriptional analysis also indicated variations in gene expression between three characteristic isolates under different environmental conditions. These results suggested that the prevalence of S. aureus strains on food-processing surfaces is above all conditioned by the ability to adapt to the environmental stress conditions present during food production. These findings are relevant for food safety and may be of importance when choosing the safest environmental conditions and material during processing, packaging, and storage of seafood products. © 2012 Springer Science+Business Media New York.

Sorheim O.,Nofima AS | Hoy M.,Nofima AS | Hoy M.,ABB
Meat Science | Year: 2013

Premature browning (PMB) in the centre of cooked hamburgers and beef loin (M. longissimus dorsi) steaks was assessed visually and instrumentally. Rosemary extract, ascorbic acid, sodium lactate, polyphosphate or lingonberry juice were added to freshly ground beef with predominant oxymyoglobin, and hamburgers were cooked to 62°C. In general, the tested ingredients did not reduce the extent of PMB in hamburgers, but polyphosphate tended to reduce PMB due to increased pH. Control burgers made of vacuum packaged meat with deoxymyoglobin were cooked to 62, 69 and 75°C, and did not express PMB. Beef loins were injected with a solution of sodium lactate, polyphosphate and sodium chloride. Loin steaks were stored under 75% O 2/25% CO 2 for 5days and also cooked to 62°C. Injected steaks had less PMB than non-injected controls, but of a low magnitude unlikely to influence the perception of doneness. The study demonstrated that anaerobic packaging is the most efficient measure to avoid PMB in beef. © 2012 Elsevier Ltd.

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