Protein contents: Results show that protein contents in fresh fish flesh was not significantly different from one species to another. Values obtained varied from 18.81±1.55-21.23±1.50 g/100 g Arius parkii and Silurus glanis, respectively. These values are comparable with those of Medale who obtained an average protein content of 18.5 g/100 g for 540 fish species specimen. These researchers concluded that the very broad fish taxonomic diversity did not significantly influence the content and composition of muscular proteins. In effect, other studies revealed that muscular proteins content does not vary significantly with the age and is not influenced by the composition of fish feed (Kaushik and Luquet, 1979).
Moreover, fish from Lagdo exhibit protein contents quite similar to those of sheep meat (17.2 g/100 g), cow meat (19.6 g/100 g) and pork (19.4 g/100 g) (Hladik and Leigh, 1993). Heat treatment, sun-drying and smoke-drying, increased protein contents. Important amounts were obtained: from 51.68±2.62-75.72±3.66 g/100 g with the highest value always recorded for smoke-dried products. The increase in protein contents may be due to product dehydration which concentrated proteins, thus increasing the nutritional value of Lagdo fish. Similar results were obtained by Thot and Pothast (1984).
Fats contents: Fresh fish flesh appeared to be relatively low in fats. Modest concentrations were obtained and varied between 0.57±0.01 and 1.51±0.03 g/100 g for Tilapia nilotica and Silurus glanis, respectively. Considering their fats contents, the three studied species could be considered as thin fish so as cod or haddock which fats contents is <1%. These values are slightly raised by sun-drying and smoke-drying.
The greatest increase was observed on the sun-dried flesh of Arius parkii (3.31±0.38 g/100 g). The low increase in fats contents could be explained by possible losses during various heat treatments. Furthermore, studies revealed that lipid contents fluctuate considerably with age, feed and sexual cycle of fish.
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