Ragnar L. Olsen

Liquid Loss as Effected by Post mortem Ultrastructural Changes in Fish Muscle: Cod (Gadus morhua L and Salmon Salmo salar

This study was performed in order to assess the effect of early post mortem structural changes in the muscle upon the liquid-holding capacity of wild cod, net-pen-fed cod (fed cod) and farmed salmon. The liquid-holding capacity was measured by a low speed centrifugation test. Transmission electron microscopy was used to discover ultrastructural changes both in the connective tissue and in the myofibrils. Differential scanning calorimetric thermograms of the muscle proteins were recorded to elucidate whether fundamental differences did exist between the proteins of the raw material tested. Multivariate statistics were used to explicate the main tendencies of variations in the thermograms. The salmon muscle possessed much better liquid-holding properties than the cod muscle, and wild cod better than fed cod regardless of the storage time. Both fed cod and farmed salmon, underwent the most severe structural alterations, probably caused by the low muscle pH values. The higher liquid-holding capacity of the salmon muscle was related to species specific structural features and better stability of the muscle proteins. The myofibrils of the salmon muscle were denser and intra- and extracellular spaces were filled by fat and a granulated material. The differences in thermograms of muscle from wild and fed cod were largely explained by the variations in pH. The severe liquid loss of fed cod is due to a low pH induced denaturation and shrinkage of the myofibrils. Post mortem degradation of the endomysial layer and the sarcolemma may have further facilitated the release of liquid.

Seasonal variations in chemical and sensory characteristics of farmed and wild Atlantic halibut (Hippoglossus hippoglossus)

Abstract Quality characteristics of farmed and wild halibut from the period of May to December were investigated by measuring liquid-holding capacity, muscle pH, fatty acid (FA) composition and by a quantitative descriptive sensory analysis. The liquid-holding capacity of farmed halibut muscle varied throughout the season. A significant increase in liquid loss was observed in July and August, indicating that the quality is lower in these months. The liquid loss (LL) increased with decreasing pH at pH lower than 6.3, whereas at higher pH, the LL was independent of pH. In the farmed halibut, the average muscle pH 6.14 varied from 5.90 to 6.64. Average muscle pH in the wild halibut (6.41) varied from 6.33 to 6.49. The fat content in the wild halibut muscle was

Effects of dietary marine oils and olive oil on fatty acid composition, platelet membrane fluidity, platelet responses, and serum lipids in healthy humans

The influence of various dietary marine oils and olive oil on fatty acid composition of serum and platelets and effects on platelets and serum lipids were investigated as part of an extensive study of the effects of these oils on parameters associated with cardiovascular/thrombotic diseases. Healthy volunteers (266) consumed 15 mL/d of cod liver oil (CLO); whale blubber oil (refined or unrefined); mixtures of seal blubber oil and CLO; or olive oil/CLO for 12 wk. In the CLO, seal oil/CLO, and whale oil groups, serum levels of eicosapentaenoic acid (EPA) were increased. In platelets, EPA was increased in the CLO, seal/CLO, and olive oil/CLO groups. The localization of n-3 polyunsaturated fatty acids in the triacylglycerols did not seem to influence their absorption. Intake of oleic acid is poorly reflected in serum and platelets. No significant differences in triacylglycerols (IG), total cholesterol, or high density lipoprotein cholesterol were observed, even though TG were reduced in the CLO, CLO/seal oil, and whale oil groups. Mean platelet volume increased significantly in both whale oil groups and the CLO/olive oil group. Platelet count was significantly reduced in the refined whale oil group only. Lipopolysaccharide-stimulated blood tended to generate less thromboxane B2 in CLO, CLO/seal, and CLO/olive groups. The whale oils tended to reduce in vivo release of β-thromboglobulin. In conclusion, intake of various marine oils causes changes in platelet membranes that are favorably antithrombotic. The combination of CLO and olive oil may produce better effects than these oils given separately. The changes in platelet function are directly associated with alterations of fatty acid composition in platelet membranes.

Purification and characterization of two trypsin-like enzymes from the digestive tract of anchovy Engraulis encrasicholus.

1. Two trypsin-like enzymes, designated Trypsin A and B, were purified from the pyloric caeca and intestine of anchovy by (NH4)2SO4 fractionation, affinity chromatography (Benzamidine-Sepharose-6B) and ion exchange chromatography (DEAE-Sepharose). 2. Both trypsins catalyzed the hydrolysis of N-benzoyl-DL-arginine p-nitroanilide (BAPNA), p-tosyl-L-arginine methyl ester (TAME), casein and myofibrillar protein and they were inhibited by several well established trypsin-inhibitors. 3. The enzymes had mol. wts of 27,000 (Trypsin A) and 28,000 (Trypsin B). Their isoelectric points were about 4.9 (Trypsin A) and 4.6 (Trypsin B) and they had similar amino acid composition. 4. The enzymes had a pH optimum of 8-9 for the hydrolysis of BAPNA and of 9.5 for the digestion of casein and myofibrillar protein. Their activity and stability were affected by calcium ions. 5. Trypsins A and B resemble other fish trypsins in their mol. wt, pI, kinetic properties and the instability at low pH and they are similar to bovine trypsin in their dependence of Ca2+ for activity and stability.

Catalytic properties and chemical composition of pepsins from Atlantic cod (Gadus morhua)

1. Three pepsins were purified from the gastric mucosa of Atlantic cod (Gadus morhua). 2. The enzymes, called Pepsin I and Pepsin IIa and b, had isoelectric points 6.9, 4.0 and 4.1, respectively, and digested hemoglobin at a maximal rate at a pH of approximately 3. 3. They resembled bovine cathepsin D in being unable to digest the mammalian pepsin substrate N-acetyl-L-phenylalanyl-3,5-diiodo-L-tyrosine. 4. Specificity constants (kcat/Km) for the cod pepsins were lower than for porcine pepsin, and they expressed higher substrate affinity and physiological efficiency at pH 3.5 than at pH 2. 5. The cod pepsins are glycoproteins, and their amino acid composition resembles that of porcine cathepsin D more than that of porcine pepsin. 6. The N-terminal sequence of Atlantic cod pepsins is substantially different from that of porcine pepsin. This indicates a significant evolutionary gap between fish and mammalian pepsins.

Post-mortem structural characteristics and water-holding capacity in Atlantic halibut muscle

Structural characteristics of seven farmed and wild Atlantic halibut muscle (5 days post mortem) were individually studied, in relation to the pH and water-holding capacity (WHC) of the muscle. Both light- and electron-microscopic techniques were used to qualitatively investigate structural attributes that influence WHC. Farmed and wild halibut with different muscle pH and similar WHC were compared as well as farmed samples having similar pH but different WHC and vice versa. Both farmed and wild halibut exhibited the same structural alterations post mortem but they appeared more pronounced in the farmed fish. Small, new fibres were seen more often in the farmed fish than in the wild fish muscle. Common structural characteristics that could be related to decreased WHC were detachment of sarcolemma, gaps in the extracellular matrix, increased intermyofibrillar space and transverse shrinkage of the cells. It was not evident whether disruptions of the myofilaments influenced the WHC or not. The results indicated, however, that low pH in combination with pronounced structural degradation influenced the WHC more than low pH in combination with minor structural degradation.

Alkaline phophatase from the hepatopancreas of shrimp (Pandalus borealis): A dimeric enzyme with catalytically active subunits

Abstract 1. 1. Alkaline phosphatase was purified to homogeneity from the cold water shrimp, Pandalus borealis. 2. 2. The enzyme is a dimeric protein with a mol. wt of 155,000. 3. 3. Contrary to other dimeric alkaline phosphatases the shrimp enzyme may be dissociated into subunits which retain enzyme activity. 4. 4. The shrimp alkaline phosphatase is completely inhibited by EDTA, but the activity can be restored to a large degree by zinc. 5. 5. The enzyme shows high stability towards SDS and 2-mercaptoethanol. 6. 6. The activity is moderately inhibited to the same extent by l -phenylalanine and l -homoarginine.

Origin and spoilage potential of the microbiota dominating genus Psychrobacter in sterile rehydrated salt-cured and dried salt-cured cod (Gadus morhua)

Salt-cured and dried salt-cured cod rehydrated using sterile water and equipment have a short shelf life at 4 degrees C due to high bacterial counts. The microbiota develops off-odours which partly can be described as musty, causing sensory rejection within 7-10 days of chilled storage. The microbiota composition was studied in a total of 38 samples obtained from 10 different, both commercial and laboratory produced, salt-cured and dried salt-cured cod products. The dominating bacterium, representing at least 90% of the total viable count in all products studied, was identified as belonging to the genus Psychrobacter; a Gram-negative, oxidase- and catalase-positive, nonpigmented, halotolerant, psychrotolerant, facultative aerobe and nonmotile bacterium. The morphology of the bacterium resembles coccobacilli and the cells occur most often in pairs. The bacterium was able to hydrolyze lipids, but not proteins. It did not produce H(2)S or TMA and the spoilage in rehydrated salt-cured and dried salt-cured cod is therefor different from what is observed in fresh cod. However, samples inoculated with Psychrobacter immobilis gave the same musty odour as spoiled control samples but earlier in the storage period and of a stronger intensity. In a field experiment, carried out to investigate the origin of the dominating bacterium, it was found that the microbiota in both sterile rehydrated commercially produced and laboratory (aseptically) produced salt-cured cod was dominated by this same bacterium. The bacterium was also isolated from cod skin mucus immediately after capture. The bacterium survived NaCl concentrations up to 25% (w/v) NaCl, stating its ability to survive during the salt-curing process. The dominating bacterium in rehydrated salt-cured and dried salt-cured cod seems to mainly originate from the fresh fish itself and not from contamination during processing.

Liquid-holding capacity and structural changes in comminuted salmon (Salmo salar) muscle as influenced by pH, salt and temperature

The loss of liquid in salmon muscle comminuted with salt was studied as a function of pH and heating temperature. A factorial experiment was designed to compare the effects of; the raw material, NaCl concentration, pH, degree of comminution and heating temperature in order to evaluate both main effects and interaction effects. The liquid-holding capacity was measured by a low speed centrifugation net test. The changes in microstructure in the samples were investigated by light microscopy using fat- and protein-staining techniques. The heating temperature, pH, NaCl concentration, variation of raw material and degree of comminution influenced liquid loss according to a second-order interaction linear model. The interaction effect between low pH, low salt concentration and high temperature was strongest. Addition of salt extracted the myofibrillar proteins and resulted in a homogeneous protein matrix with few intact fibres and uniformly dispersed fat droplets. Liquid loss was closely related to the microstructure of the comminutions. When heated above 30 °C, enlarged pores and gaps, some of them forming channels, occurred in the protein matrix. In comminutions prepared with a low salt concentration and/or a low pH the more frequent presence of pores and gaps enhanced the liquid loss.

EFFECT OF MARINE OILS SUPPLEMENTATION ON COAGULATION AND CELLULAR ACTIVATION IN WHOLE BLOOD

A study was performed to explore the effects of supplemental intake of various marine oils known to be part of the Eskimo diet. Healthy men and women (134) were randomly selected to consume 15 mL/d of oil from blubber of seal, cod liver, seal/cod liver, blubber of Minke whale, or no oil for ten weeks. Total cholesterol was unchanged in the oil groups, whereas high density lipoprotein cholesterol increased 7% in the seal/cod liver oil (CLO) group (P<0.05) and 11% in the whale oil group (P<0.005). Triacylglycerol was significantly reduced in the CLO group only. The concentration of prothrombin fragment 1+2 was reduced 25% (P<0.05) after whale oil supplementation. No change in fibrinogen or factor VIIc was detected. Tumor necrosis factor generation in lipopolysaccharide (LPS)-stimulated blood was 30% reduced after whale oil (P<0.05), but was unaffected by intake of seal or CLO. The LPS-induced tissue factor activity in monocytes was reduced to a significant degree only in the seal/CLO group (34%) and whale oil group (35%) (P<0.05). The most dramatic change in thromboxane B2 in LPS-stimulated blood was seen after whale oil intake with 44% reduction (P<0.01). Supplementation of a regular diet with a combination of seal oil and CLO and especially with whale oil seems to have beneficial effects on several products thought to be associated with cardiovascular and thrombotic diseases.