Simplified Test on the Freshness of Fish Meat III. Non-Precipitability of Hexon Base with Mercuric Chloride

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As a delicate and characteristic method for detecting the early stages of decom-position of fish flesh, we reported the coagulation test of soluble protein-like subs-tances with mercuric chloride solution. In the previous paper, it was described that the coagulum probably contains soluble protein, and also mercuric-amino-chloride but in lesser amount**. However, some questions have been, yet left whether the coagulum, contains hexon bases. To. solve this problem, the precipi-tability of mercuric chloride with hexon bases was examined in aqueous extracts of fish muscle. In the first experiment, 10 gms of putrid flesh of skipjack were ground and mixed with 1CO c.c. of distilled water, filtered off after 60 minutes. To 10 c.c. of the filtrates added 1 c.c. of 20% trichloracetic acid and the precipitates were removed; filtrates were heated on water. bath for about 10 minutes to drive out CCl3C00H as chloroform, and then cooled off. To this added 5 c.c. of 1% HgCl2. No precipitate was obtained in this treatment. (See Table 1) In the second experiment, we tried to estimate the amount of hexon bases in the filtrates which was obtained either by removing the precipitates of CCl3C00H or by giving off that of HgCl2 of the aqueous extracts of fish flesh. The marlin flesh, in this case, stored at room temperature, was observed for determining the hexon bases during the decomposition. To each 10 c.c. of the filtrates prepared as noted above, added 0.5 c.c. of conc. sulfuric acid as well as 2 c.c. of 5% phospho-tungstic acid in order to precipitate hexon bases in the solution. Nitrogen contentof the precipitates was determined by Kjeldahl method; the re ?? ults are summarized in Table 2. It is apparent that the amount of hexon base nitrogen is not much different in the filtrates of two kinds as far as the prim ry'cleavage of the muscle protein goes. (Table 2). In the light of these experiments, it may be assumed that the mercuric chloride does not react with the hexon bases in the aqueous extracts of I fish meat, further the water soluble protein is the major constituent in the coagulum as already suggested by us**. It is added : copper salts, such as copper sulfate and copper chloride, though reaction is not so delicate, may be also used. for the same purpose in stead of mercuric chloride. (Table 3).
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Simplified Test on the Freshness of Fish Meat III. Non-Precipitability of Hexon Base with Mercuric Chloride

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