• Korean Journal of Fisheries and Aquatic Sciences
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• v.12 no.4
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• pp.225-234
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• 1979

For the effective utilization of diverse and abundant resource of seaweeds in Korea as a food protein supplment, extraction conditions of water, salt, and alkali soluble proteins were investigated in previous work(Ryu and Lee, 1977: Lee et al., 1977: Lee et al., 1978). The present study as a part of the serial work was thus aimed to find the conditions of isolation and purification of extracted proteins, and to evaluate the nutritional quality of the isolated seaweed proteins in terms of amino acid composition, chemical score, protein score, modified essential amino acid index(MEAAI), and in vitro digestibility presented as pepsin-pancreatin digest residue index (PPDRI). As for the isolation of extracted proteins, TCA treatment was more effective for the proteins from rhodophyceae and Chlorophyceae while the precipitation at isoelectric point was more desirable for Phaeophyceae proteins. In amino acid composition, water soluble protein fraction was superior to the other fractions in Porphyra suborbiculata whereas both water and alkali soluble fractions seemed to bo more benefitial for Enteromorpha linza and Ulva pertusa; the extraction with alcohol-alkali mixed solvent for Undaria pinnatifida and Sargassum fulvellum. Glutamic acid and aspartic acid content was particularly high in all protein fractions examined. The total amino acid content of Porphyra suborbiculata and Enteromorpha linza was almost equivalent to that of dried whole egg although the essential amino acid content was lower. A comparative analysis was made on the inedexes between raw seaweed powder and isolated protein. Chemical score of Porphyra suborbiculata and Ulva pertusa was approximately 35 and 56 in cafes of raw powder and isolated protein respectively while only 10 to 16 for raw powder of Undaria pinnatifida and Sargassum fulvellum and 30 to 35 for their isolated proteins. Protein score of all isolated proteins was in the range of 63 to 73 which indicates that isolated protein would be mere valuable than the fern of raw seaweed powder. Digestibility by means of PPDRI was found to be extremely low in case of raw powder but it could be doubled in case of isolated protein yielding 67 to 70 for Porphyra suborbiculata and Ulva pertusa.