Liquid Holding Capacity and Structural Changes During Heating of Fish Muscle: Cod (Gadus morhua L.) and Salmon (Salmo salar)

The loss of water and fat in cod and salmon muscle was studied as a function of heating temperature from 5-70 C. The liquid-holding capacity was measured by a low speed centrifugation net test leading to the separation of released liquid. To obtain a better understanding of the liquid-holding properties, the microscopic changes of the samples were evaluated by light microscopy. Two different preparation techniques were used . Cod lost twice as much water as salmon upon beating. After an initial delay , the water loss increased at 20-35°C, attained a maximum at 45-50°C, and thereafter decreased in both fish species. Salmon muscle was more heat-stable than cod muscle. Since the main structural changes appeared in the connective tissue at low temperatures (5-40°C), the water loss at these temperatures is probably mainly due to denaturation and melting of collagen. The maximum water loss was attained when the muscle cell shrank due to denaturation of myosin. The reduced water loss at higher temperatures (50-70°C) is probably caused by aggregates of sarcoplasmic proteins stabilizing the aqueous phase

Liquid Holding Capacity and Structural Changes During Heating of Fish Muscle: Cod (Gadus morhua L.) and Salmon (Salmo salar)

The loss of water and fat in cod and salmon muscle was studied as a function of heating temperature from 5-70 C. The liquid-holding capacity was measured by a low speed centrifugation net test leading to the separation of released liquid. To obtain a better understanding of the liquid-holding properties, the microscopic changes of the samples were evaluated by light microscopy. Two different preparation techniques were used . Cod lost twice as much water as salmon upon beating. After an initial delay , the water loss increased at 20-35°C, attained a maximum at 45-50°C, and thereafter decreased in both fish species. Salmon muscle was more heat-stable than cod muscle. Since the main structural changes appeared in the connective tissue at low temperatures (5-40°C), the water loss at these temperatures is probably mainly due to denaturation and melting of collagen. The maximum water loss was attained when the muscle cell shrank due to denaturation of myosin. The reduced water loss at higher temperatures (50-70°C) is probably caused by aggregates of sarcoplasmic proteins stabilizing the aqueous phase

Evaluation of Prebiotic and Probiotic Effects on the Intestinal Gut Microbiota and Histology of Atlantic salmon (Salmo salar L.)

In the present study the impact on gut microbiology and indigenous gut histology of Atlantic salmon (Salmo salar L.) was investigated following feeding of a control and a prebiotic (EWOS prebiosal®) diet and ex vivo exposure to saline or the probiotic bacterium Carnobacterium divergens. The results showed that ex vivo exposure of C. divergens at 108 CFU ml-¹ did not cause cell damage to the intestine tract of Atlantic salmon. Furthermore, prior provision of dietary prebiotic elevated the ability of C. divergens to adhere to the epithelium or mucus layer in the proximal intestine, where culturable heterotrophic bacterial levels (which were identified as C. divergens) were elevated by 234% compared to the control. This effect was not apparent in the distal intestine. The ability of isolated carnobacteria from the ex vivo experiment to inhibit growth of two fish pathogenic bacteria (Yersinia rückeri and Aeromonas salmonicida ssp. salmonicida) was assessed. Extracellular products from all 11 of the isolated carnobacteria strains, plus the type strain Carnobacterium inhibens CCUG 31728, inhibited the in vitro growth of Y. rückeri. However, only extracellular products from C. divergens isolate 57 inhibited the growth of A. salmonicidapublishedVersio

Bjørn Christiansens vitenskapelige arbeider

Bibliography of the works of Bjørn Christianse

Pathophysiological effect of chronic and acute stress in Atlantic salmon, Salmo salar (Actinopterygii: Salmoniformes: Salmonidae)

The knowledge on the effect of different stress factors on Atlantic salmon, Salmo salar Linnaeus, 1758, is far from complete and therefore we decided to find out how the low water level stress could effect pathophysiological parameters such as: plasma cortisol level, haemoglobin, haematocrit, chloride (Cl−), sodium (Na+), osmolality, lactate, and glucose in this fish; and how this stressor affects the gut morphology. Two hundred and four juvenile Atlantic salmon were randomly distributed into six fibreglass tanks and divided into two groups: group 1 (control) and group 2 (low water level tress). The low water level stre did not affect growth performance and the pathophysiological parameters. Light- and transmission electron microscopy evaluations of the pyloric caeca and the distal intestine revealed that chronic stress had no effect on gut morphology. Low water level stress had no clear effects on pathophysiological parameters and gut morphology of Atlantic salmon

Histological and bacteriological changes in intestine of beluga (Huso huso) following ex vivo exposure to bacterial strains

In the present study the intestinal sac method (ex vivo) was used to evaluate the interactions between lactic acid bacteria and staphylococci in the gastrointestinal (GI) tract of beluga (Huso huso). The distal intestine (DI) of beluga was exposed ex vivo to Staphylococcus aureus, Leuconostoc mesenteroides and Lactobacillus plantarum. Histological changes following bacterial exposure were assessed by light and electron microscopy. Control samples and samples exposed only to Leu. mesenteroides and a combination of Leu. mesenteroides and Staph. aureus, had a similar appearance to intact intestinal mucosal epithelium, with no signs of cellular damage. However, exposure of the DI to Staph. aureus and L. plantarum resulted in damaged epithelial cells and disorganized microvilli. Furthermore, 16S rDNA PCR denaturing gradient gel electrophoresis (PCR-DGGE) was used to investigate the adherent microbiota of distal beluga intestine. Several bacterial species were identified by DGGE in the present study that have not previously been identified in beluga