Partial characterization and nutritive value of proteins from pacu (Colossoma mitrei, Berg 1895)

The edible portion (fillet) of pacu (Colossoma mitrei), a freshwater fish from the south of Brazil, was composed of 67.7% water, 13% protein, 17.2% total lipids, and 1.3% minerals. The muscle proteins were composed of 64.3% myofibrillar, 25% sarcoplasmic, and 8% stroma proteins. Simple polyacrylamide gel electrophoresis revealed six protein bands in the sarcoplasmic fraction; SDS-polyacrylamide gel electrophoresis revealed eight protein structural units with molecular weights ranging from 4000 to 149 000. Total protein nutritive value was similar to that of casein in terms of PER and growth-promoting capacity. Full-fat fillet protein did not differ from casein (p = 0.05) with respect to apparent digestibility and net protein utilization but was inferior to casein in the apparent biological value. On the other hand, defatted fillet protein was inferior to casein (p = 0.05) in all of the three indices calculated.