RESUMEN
Fish protein concentrate (FPC) from river Nile bolti fish (Tilapia nilotica) was prepared and compared with commercial FPC and fresh bolti fish flesh. Fish meal (FM) from bolti fish offals was prepared and compared with commercial FM and also fresh bolti fish flesh. FPC from bolti fish showed a higher crude protein content but less fat, ash, calcium and sand than the commercial sample, while FM from bolti fish showed a higher content of ash and phosphorus than commercial FM but was nearly similar in crude protein, fat, calcium and sodium chloride. FPC from bolti fish had a higher content of lysine, arginine, aspartic acid, glycine and glutamic acid and a lower content of the other free amino acids. The bolti fish FM had a lower content of total amino acids and the contents of the free amino acids cysteine, glycine, aspartic acid, serine, alanine, valine, and methionine increased slightly. The yield was 12% for FPC and 19.5% for FM. Coliform bacteria were not present in both FPC and FM from bolti fish. Low moisture contents of FPC and FM were essential for preventing microbiol growth and to attain a good keeping quality. The FPC and FM from bolti fish reached moisture equilibrium and stopped increasing in weight within 144 to 192 h.
Asunto(s)
Harina de Pescado/análisis , Productos Pesqueros/análisis , Proteínas/análisis , Aminoácidos/análisis , Animales , Bacterias/aislamiento & purificación , Fenómenos Químicos , Química , Egipto , Microbiología de Alimentos , Conservación de Alimentos , Hongos/aislamiento & purificación , Humedad , Factores de TiempoRESUMEN
The shelf life of bolti fish (Tilapia nilotica) caught in the river Nile, has been successfully prolonged for about 9 days by dipping in tetracycline (TC) or nisin solution followed by refrigeration, although the initial microbial contamination in the fresh fish was very high. The caught fish were gutted and treated with 10 and 20 ppm TC solutions for 10 and 15 min by dipping, and with 500 and 1000 R.U. nisin/g fish for 20 and 30 min. The treated and control fish samples, were stored and refrigerated at (4 +/- 1) degree C for 12 days. Total bacterial counts, the most probable number of coliform bacteria and lactic acid bacteria in the fish treated with TC or nisin, were lower than those of the control, especially at 20 ppm TC, 15 min dipping, and 1000 R.U. nisin/g, 30 min. Further more TC was more effective against yeasts and moulds. This result suggest that antibiotics would help in transporting chilled fish from the highdam lake in Aswan to Cairo (about 900 km). According to the present results it may be recommended to use the antibiotic TC, with the concentration of 20 ppm for 15 min dipping, for prolonging the shelflife of bolti fish. The presence and increase of coliform bacteria in fish, draw the attention to the necessity of hygienic measures when dealing with such fish until to the consumption.