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The aim of the investigation was to establish the functional properties of muscle protein isolates from Baltic cod (Gadus morhua) spine which were also compared with a commercially available pork protein preparation. The muscle proteins were extracted in mild condition with 0.1M NaOH solution at 4°C and subsequently were precipitated at pH 4.5. The amino acid composition of protein isolates is similar to fresh muscle protein. At the basic pH values, the obtained preparation is almost three times more soluble than the commercially available pork protein. Cod proteins were in 25 and 90% solubilized at pH 8 and 12, respectively. At these pH values, after an increase of the ionic strength of the solution to 0.35, the protein solubility decreased about 10 and 15%, respectively. Spinal proteins at a pH range of 6-12 have a 16-time higher foaming capacity than that for pork proteins. The obtained proteins also have a two-times lower oil holding capacity and almost 5.5-times lower water holding capacity in comparison with the commercial preparation. The preparation of muscle proteins from Baltic cod had an ability to hold 0.26 g oil or 0.94 g water per g of protein. Its quite good functional properties encourage continuing research on the deodorization method. After deodorization this protein preparation could find an application in the food industry.
The aim of the study was to establish the optimum conditions for recovering non-collagen proteins from the backbones of cods by solvent extraction. The proteins were extracted in three different ways: twice in 24 h with 5% sodium chloride or 0.1 M sodium hydroxide solution, or firstly using 5% sodium chloride solution over 24 h, and then 0.1 M sodium hydroxide solution in 24 h. Different ratios of backbone to solution were tested, 1 : 2; 1 : 4; 1 : 6; 1 : 8; 1 : 10; 1 : 12. All procedures were performed at 4°C. 0.1 M solution of sodium hydroxide was more effective in extracting protein than 5% solution of sodium chloride. A 100% yield of non-collagen protein was recovered from fresh backbone by double 24 h extraction with sodium hydroxide solution, while this was 70%with sodium chloride solution. About 80% of the protein was soluble when extraction was conducted in the first stage with sodium chloride solution and then with sodium hydroxide solution. After 5 months of storing the backbone at -18°C, protein recovery decreased by about 40% for sodium chloride solution and about 20% for sodium hydroxide solution, and about 30% for mixed extraction. The extraction yield had no influence on the ratio of extracted material to solution. Collagen losses during extraction did not exceed 0,4%.
Enzymatic hydrolysis was conducted to recover the potentially addible high protein hydrolysate from cod backbones. The commercially available alcalase and trypsyne was used for hydrolysis at enzyme concentrations of 2.5; 5; 10; 15; 20; 30 and 40 mg/g backbones. The enzymatic deproteinization was conducted for 24 and 48 h. All procedures were performed at pH 7.0 and 4°C. The yield of enzymatic hydrolysis increases with the growth of trypsine and alcalase concentration up to 20 and 10 mg/g backbone, respectively. The increase of these values did not influence the yield of enzymatic deproteinization. After the treatment by trypsyne, maximum recovery of protein from cod backbone was 60%, while by alcalase it was 55%. The yield of enzymatic hydrolysis was the same after 24 and 48 h. Collagen losses did not exceed 0.2%.
The causative agents of health problems of rainbow trout from a fish farm were investigated by parasitological and anatomo-pathological study of affected fishes. The anatomo-pathological changes in gills, swim bladder, kidney, and especially the deformations of backbone are described. The numerous trophozoites of unidentified species of Myxosporea, occurring in all damaged tissues are suspected to be a causative agent of the disease and mortality in the fish farm under study.
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