Simplified Test on the Freshness of Fish Meat:(2) Reaction of Mercuric Chloride on the Soluble Protein

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The Walkiewicz's method to test the freshness of beef was also applicable to the meat of whale and some fishes. (Amano & Uchiyama1) 1948) The present paper embodies some experiments concerning the following items: 1) Time required to finish the extraction of soluble nitrogen from ground fish flesh. 2) Amounts of water required to extract nitrogen from a given quantity of the ground meat. 3) Amounts of soluble nitrogen remained in the residue. 4) Coagulation of nitrogen by HgCl2 in the course of decomposition. (See Fig. 2 and Table 3 & 4). 5) Amounts of coagulable nitrogen by HgCl2 when the meat is subjected to a dilute alkaline extraction. It is apparent in Fig. 1 that the time required to finish extraction of nitrogen will be less than 30 minutes regardless of the mechanical agitation. We have confirmed (Table 1) that the quantity of extracting water has no relation to the amount of nitrogen freed from ground meat, viz. the meat has a constant amount of soluble nitrogen in a certain circumstance. It has also been shown that with the repeated extraction of ground meat, the soluble nitrogen had been carried away almost completely by the first treating, with no soluble nitrogen in the residue of flesh being found. From the proceeding experiments it may be concluded that the preparation of the test solution can be readily made within 30 minutes. We often observed that the coagulable nitrogen by HgCl2 occurs at the exact point where the meat begins to decompose in a degree containing 30 mgms of volatile nitrogen with. the PH value 6.0 to 6.2. Therefore we made extract of the freshest meat with dilute alkaline solution, and PH value of the filtered extract was made to range from 6.2 to 6.4, the values usually found in the tainted fish extractive. Adding 1.0% HgCl2 to the filtrate the amount of nitrogen precipitated was compared to that of tainted meat. (Table 3 & 6) These facts indicate that HgCl2, do not react on the water soluble protein, if very fresh meat is treated, but in the filtrate of decaying flesh it positively reacts. This may be explained as follows: the reaction in the latter case takes place through the similar course as in the case of alkaline treated extract. The present simplified method to test the flesh, the writers recommend, will be applied in the food fish inspection in which hitherto only organoleptic examination has been practiced.
社団法人日本水産学会の論文

Simplified Test on the Freshness of Fish Meat:(2) Reaction of Mercuric Chloride on the Soluble Protein

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