Extractability of Proteins from Fish Skeletal Muscle at Low Ionic Strengths

Abstract

The extractability of proteins from fish muscle homogenates was investigated at ionic strengths ranging between p 0 and 0.3 (pH 6.8∽7.0; ratio of muscle to extractant, 1: 30) with 18 species of teleosts. Species variations were observed in the extraction patterns obtained between p 0 and 0.05. As the ionic concentration was raised from p 0 to 0.05, the amount of extractable protein increased rapidly in dark meat fish (migratory fish) such as sardine or chub mackerel and increased slowly in fish such as horse mackerel or lizard fish which are considered to be intermediate between dark and white meat fish. In white meat fish (bottom fish) such as Alaska pollack or nemipterid, however, the extractabilities more or less decreased in the range of p 0.025∽0.05. Such differences between dark and white meat fish are attributable to a fraction eluting at Kav 0.2∽0.3 on Sephadex G 200 filtration which is abundant in the sarcoplasm of the former (chub mackerel), and the greater solubilization of myofibrils from the latter (Alaska pollack) at ionic strengths of μ 0.025. From the results, μ0.05 was recommended as the optimum concentration for extracting sarcoplasmic proteins from either dark or white meat fish. The values of 0.05μ extractable protein nitrogen obtained in this study closely corresponded with those of non-protein nitrogen, the latter being an accepted marker for distinguishing between the two groups of fish. © 1976, The Japanese Society of Fisheries Science. All rights reserved.