Leif Rein Njaa

Catalase, glutathione peroxidase and superoxide dismutase in different fish species

Abstract 1. 1. The activities of catalase, glutathione peroxidase and superoxide dismutase were determined in extracts from nine different species of fish. 2. 2. The localization of these enzymes in different tissues were determined in saithe and mackerel. 3. 3. A relationship seems to exist between the levels of glutathione peroxidase and superoxide dismutase and the content of methionine sulphoxide in samples of fish kept in cold storage.

Autolysed fish silage as a feed ingredient for atlantic salmon (Salmo Salar)

Abstract 1. 1. Fish silage made from saithe stored for 2 and 5 months was compared to raw minced saithe as a replacement for parts of the dietary feed protein for Atlantic salmon (Salmo salar). 2. 2. Weight gain and feed utilization were better in the fish fed the silage stored for 2 months and the raw mince than fish fed the silage stored for 5 months. These fish also showed somewhat better protein utilization. 3. 3. Those fish fed the most hydrolysed feed nitrogen, stored less fat in carcass and fillets, resulting in higher amounts of protein.

Growth of young rats on diets based on fish silage with different degrees of hydrolysis

Abstract The effect of storage for up to 1 year on the nutritional value of ensiled cooked and non-cooked minced capelin was determined in growth experiments with young rats. Minced fresh capelin of the same batch was also included. Cooked silage came out best after the storage of 1 year showing both better growth and protein efficiency ratio (PER). There were no significant differences in apparent digestibilities. Rats given the uncooked silage accumulated more glycogen in the liver than the rats given the cooked silage diet ( p The rats given raw minced capelin performed worse than the rats given the silages of up to 180 days of storage, but they performed better than those with 1 year of storage. This was probably due to the procedure used for mixing the diet.

Effect of local processing methods (cooking, frying and smoking) on three fish species from Ghana: Part 2—Amino acids and protein quality

Abstract The effect of processing methods (cooking, frying and smoking) on the amino acid composition of Sardinella sp., Dentex sp. and Tilapia sp. was studied. Protein quality, as expressed by AD, TD, NPU and Bal% was also investigated. All the processed fish had good quality protein; as expressed by their high AD, TD and NPU. The good quality of the processed fish was further supported by the amino acid composition. Cooked fish was better absorbed than fried and smoked.

Effect of a Bangladeshi home-cooking procedure on the amino acid content, trypsin inhibitor activity and in vitro digestibility of some legume seeds

Raw and cooked samples of cultivars ofLens esculenta (Lentils),Pisum sativum (peas),Phaseolus vulgaris (beans),Phaseolus aureus (navy beans)Cicer arietnum (gram), andLathyrus sativus (dhal) as well as precooked commercial products were analysed for amino acids, trypsin inhibitor activity and in vitro protein digestibility. Of the fifteen samples used in the study one lentil sample, one pea sample, two gram samples and one sample of khesari dhal were from Bangladesh, one gram sample was from Sri Lanka. The other samples were obtained either in shops in Norway or from an industrial firm. The latter were also obtained precooked and dried. The two samples obtained in shops were used with hull and dehulled.

Total volatile nitrogen — A quality criterion for fish silage?

Abstract Total volatile nitrogen (TVN) consisting mainly of trimethylamine (TMA) and ammonia (NH 3 ), is used as a quality criterion for fish meal and fish meal raw material. Therefore, the significance of TVN and of the NH 3 portion of it as quality criteria for fish silage were studied. Such criteria are required to ensure a wider use of silage in fish feed. Formic acid silages were prepared from fresh raw material of mackerel and of capelin, the latter with varying amounts of acid. In properly preserved silage (stable pH) TVN and NH 3 -N increased moderately during storage and amide-N (from glutamine and asparagine) decreased at the same rate. Amide-N was taken to be the difference between NH 3 -N before and after weak hydrolysis. The amino acid composition was not significantly affected. As asparagine and glutamine are considered to be dispensable amino acids, this is not expected to affect the nutritional value of the silage. When acid addition was too low, the pH increased during storage and there were large increases in TVN and NH 3 -N but a slight decrease in amide-N similar to that found in the other silages. Furthermore, the amino acid composition was affected; arginine and tyrosine seemed most vulnerable. We conclude that amide-N from glutamine and/or asparagine is a major source of the NH 3 formed in properly preserved silage during storage. TVN is thus of limited value as a quality criterion for fish silage.

Protein, amino acids and some major and trace elements in Thai and Norwegian mushrooms

Six edible Thai mushroom species were analysed for protein, in vitro protein digestibility, amino acids and major and trace elements. The results for protein and amino acids were discussed relative to the contents in Thai rice. The contents of mineral elements showed great variation, in agreement with literature data. Two samples (Hunukao and Hom) were rich in calcium and one (Phang) was rich in iron and copper. For comparison results for samples of edible mushrooms obtained in Norway were included.

Oxidation of methionine. Effects of hydrogen peroxide alone and in combination with iodide and selenite

Abstract The oxidation of methionine by hydrogen peroxide, and the influence of iodide, pH, amino acids and selenite were studied with free methionine and with casein and fish fillet protein. The concentration levels tested ranged from 0·05 m m to 3·0 m m . Hydrogen peroxide oxidation was not influenced by pH in the range 5·0 to 8·0; at pH 8·5 the rate of oxidation was increased. When iodide was added in amounts equivalent to or less than the amounts of H2O2, the reaction was accelerated with free but not protein-bound methionine. At higher levels iodide inhibited the oxidation. An amino acid mixture and proteins inhibited the effect of iodide; this effect seemed to be due to tryptophan. Selenite also accelerated the effect of H2O2, both with free and with protein-bound methionine. Cu++ catalysed the oxidation by H2O2 at low reactant concentration but not at the higher levels. The reaction between methionine and H2O2 seemed to be of first order with respect to both reactants.

Antioxidant properties of methionine esters.

DURING feeding experiments we have found that 0.5 percent methionine in a semisynthetic diet containing 12 per cent cod liver oil prevents yellow discoloration of the diet and also the destruction of vitamins A and E (refs. 1–3). We have also studied the antioxidant properties of methionine and some derivatives using simple manometric techniques4 and have recorded the near infrared spectrum of CCl4 extracts of the semisynthetic diet. The spectrophotometric data showed a relatively constant peak at 2.34µ and a variable peak at 2.88µ which increased as oxidation progressed, permitting use of the ratio of absorptions at these two wavelengths as an additional measure of oxidation. Using both criteria hydrochlorides of the methyl and ethyl esters of methionine showed unique properties. In contrast to other compounds which were tested there were rapid but relatively small initial changes followed by extended periods in which only very slow changes took place. The esters therefore seemed to be transformed to antioxidant compounds acting in a similar way to butylated hydroxy toluene (BHT).

Oxidation of methionine: Effect of ascorbic acid autoxidation

Abstract Free methionine is oxidised in solutions containing ascorbic acid. For this oxidation to take place, molecular oxygen is required and trace amounts of metal ions catalyse the reaction. Our results indicate that ascorbic acid must autoxidise before reacting with methionine. Catalase, histidine and scavengers of hydroxyl radical (benzoic acid and ethanol) inhibit the reaction. The superoxide anion is not involved in the reaction as superoxide dismutase did not affect the oxidation rate. Dehydroascorbic acid also oxidises methionine, but at a much slower rate than ascorbic acid. In the presence of ascorbic acid, the main product in the reaction is methionine sulphoxide, but other products are also formed. Peptide-bound methionine is oxidised to a much lesser extent than free methionine.