冷凍メカジキの緑變現象に關する研究第1報緑變肉よりイソ吉草酸類似物質の分離

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The problem of green discoloration of frozen swordfish has affracted the attention of frozen food packers for several years. In 1948, about thirty per cent of the total production was found to be “green meat” and was rejected as unfitted for marketing. The greened part of the flesh gives disagreable smell which resembles that of sour kraut or sometimes foul cheese. The writer assumed that one of the components of this smell might be derived from some volatile acids and tried to detect such acids in the discolored part of frozen swordfish. Materials used … Meat flakes of frozen swordfish, collected from the green parts of the round fish stored in Shibaura Cold Storage Co., Tokyo, were introduced into the writers laboratory on 17 Jan. 1949. This sample showed characteristic foul cheese-like smell and contained volatile base nitrogen from 22mgms to 30mgms per 100gms of the meat. Another sample was obtained from Tokyo Cold Storage Co., Tokyo, on 7 Jan. 1949, and 13.5mgms of volatile base nitrogen and 0.8mgms of hydrogen sulfide were found in this case. Organoleptic test showed that the latter sample was in less advanced stage of decomposition than the former. Method of isolation of volatile acids from the fish meat Fifty gms of the chopped meat were taken, to which were added 200c.c. of distilled water and 15c.c. of 85 per cent phosphoric acid. Then the mixture was subjected to steam distillation. 200c.c. of the distillate were collected in a beaker and treated with 0.5gms of calcium hydroxide to fix volatile acids as calcium salts. After this, the whole content was evaporated to dryness on water bath. To separate alcohol soluble acids, the film-like calcium salts, thus obtained were extracted with 10c.c. of ethyl alcohol. After one hour standing, alcoholic portion was filtered off and the filtrate was tested for propionic, butyric and iso-valeric acid, and the residue for formic acid, under a petrographic microscope after Behrens-Kley. Detection of propionic acid … A few c.c. of the filtrate was transferred on hole slide glass, to which were added 10mgms of barium acetate, but no precipitate was produced, even by the help of petrographic microscope crystal of barium propionate could not be observcd. Detection of butyric acid … To another portion of the filtrate were added 10mgms of copper nitrate and one drop of 20 per cent acetic acid. On standing for several hours, small amount of crystals deposited. The crystals were collected from the mother liquor and washed with distilled water repeatedly. The combined washings and the mother liquor were gently thickned on water bath. The concentrated solution was dried in dessicator, and examined under a petrographic microscope. But not a single crystal of copper butyrate was found. Detection of iso-valeric acid … The sparingly soluble crystals, obtaind by adding copper nitrate and acetic acid, separated from mother liquor and washed, were redissolved in few drops of acetic acid and recrystallised by liberating the acid at room temperature. The recrystallisation was repeated for three times. The photomicrographs of the crystals were shown in Plate 1-5. Detection of formic acid … … The residue of calcium salts treated with alcohol was dissolved in a few c.c. of distilled water, and filtered. To the filtrate were added 10mgms of cerium nitrate, however, no cerium formats was observed in this treatment. Comparison of the isolated crystal with copper iso-valerate recorded in Behrens-Kleys description1) The crystal obtained by the writer agrees with Behrens-Kleys description in the following points 1) The dichroitic character of the crystal cannot be observed under a petrographic microscope. 2) Sometimes there appear hexagonal plates which measure about 30microns in length.
公益社団法人日本水産学会の論文

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天野慶之
水産試驗場

冷凍メカジキの緑變現象に關する研究第1報緑變肉よりイソ吉草酸類似物質の分離

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