0023-6152

AA00247166

22590

査読無

I. Chemical Changes of Muscle Proteins in Canning (1) The muscle proteins of some hens, various fishes and certain animals were prepared as samples for the purpose of studying what changes take place in the muscle proteins at the time of canning meats under pressure and heating. The materials were sealed in glass-tubes and heated at 130-140℃ for one hour, and changes of materials were studied. (2) The hydrogen ion concentration of all of the proteins showed a tendency to approach toward the neutral point. (3) About 20 per cent of the protein nitrogen was transformed by heating to peptone, peptide, and amino acid nitrogens. The formation of soluble nitrogen compounds, such as these, is considered to cause a speedy putrefaction of contents of an opened can. (4) As the results of ciementary analyses of carbon, hydrogen, nitrogen, sulphur and phosphorus, it was found that the quantities of nitrogen and sulphur contained in the proteins generally decreased by heating, and the changes were more marked the higher the values of pH. There was no appreciable change in phosphorus when the solution was neutral, but its amount decreased when solution was acidic or alkaline, and hence the percentage of carbon increased. (5) The quantities of NH_3 and H_2S generated by heating were greater in proportion to the values of pH of the solutions. This results explains the fact that, when the tin of cans are bad and the pH of the contents is high, the contents of the can deteriorate more readily and the colour changes to black. (6) As the results of the analyses of the proteins by the Van SYLKE method, the decrease of the total nitrogen, ammonia nitrogen and cystine nitrogen and the increase of melanine nitrogen were detected especially when the pH value increased. The quantitities of cystine, arginine, histidine and lysine contained in the materials showed a tendency of decrease in all three cases and the same tendencies were very remarkable on cystine at the higher value of pH and on lysine at the lower. (7) Tryptophane by the May-Rose method and the tyrosine by the Falin-Denies method were quantitatively analyzed, and the decrease of these substances by heating were very insignificant. (8) The test for proline was made by the Fisher-Bechner method, but no decomposition by heating was observed. (9) Cysteine and cystine were analyzed quantitatively by the OKUDA-KATAI method, and it was found that a part of any one of these acids aiways changed to the other acid by heating. But the sum of the two always decreased, and the decomposition of both of these acids was remarkable at the higher value of pH, and the decomposition of cysteine was greater than that of cystine. (10) A part of the protein-sulphur changed by heating to hydrogen sulphide, other sulphides, sulphuric acid and soluble organic sulphur, and the quantities of these substances generated were greater at the higher pH of the solutions, as in the case of the decompositions of cysteine and cystine. II. On the Contents of Gases and Metals in Storaged Cans The experiments were chiefly carried out with canned beef of different ages of storage, from 1 to 15 years, were as follows: 1) Among gases contained in cans examined, the quantity of nitrogen was the largest in the majority of the cans, but in some old cans the amount of hydrogen was frequently more than that of nitrogen. 2) The proportion of oxygen as compared to that of nitrogen was much smaller than it is in the air. 3) The content of carbon dioxide in cans was larger than that in the air, but it did not increase appreciably during the storage of the cans. 4) Free ammonia and hydrogen sulphide showed only traces. 5) The concentration of hydrogen ion of the canned meats showed almost no change in storage. 6) The contents of iron and tin in both canned beef and fish were nearly proportional to that of hydrogen in the cans which was produced by corrosion of -can-materials. But in the case of crab meat packed in the cans which are covered inside with lacquer, almost no increase of the contents of iron, tin and hydrogen was observed. 7) Unusual increase of hydrogen gas in some very longstored beef-cans sometimes gave rise to the so called "blown" cans, in which the ends become convex, and arc apparently analogous to the spoiled cans dilated by the pressure at carbon dioxide produced by the action of bacteria upon the contents. III. Carbon Dioxide and Hydrogen Gasses Produced at Canning and in Storage In the present case, instead of commercial cans, sealed glass tubes containing a certain meat, tin and iron powders, and solutions of different hydrogen ion concentration were used. 1) The production of carbon dioxide during canning increased a little more, as a rule, in the presence of iron than in the presence of tin alone. And also the longer the time of heating the more was the increase. 2) The production of carbon dioxide during storage, gradually increased in the presence of tin alone, but decreased in the presence of iron. The decrease seems to be due to the fact that carbon dioxide produced by gradual oxidation acts on iron to make iron carbonate and hydrogen. 3) The production of carbon dioxide seems to have some relation with the hydrogen ion concentration of meat-juice and the kind of meats, but the relation with the freshness of the meat is not definite. 4) The production of hydrogen is chiefly due to the presence of iron but only slightly to that of tin. In the presence of iron, the production had an intimate relation with the hydrogen ion concentration of meat-juice, the stronger being the concentration the more the production. The production increased proportionally to the length of time of heating in canning, and to the period of storage of cans. 5) The kind and freshness of meats have more or less influence upon the production of hydrogen from can-material. 6) The quantity of carbon dioxide produced was generally very small as compared to that of hydrogen. IV. Protein, Fat and Nutritive Value of Storaged Canned Meats. The present investigation deals with the chemical changes of the proteins and fats, and also the nutritive value of meats in cans which have endured long storage. The results of the experiments carried out with canned meats of different ages of storage were as follows :- 1) The proteins obtained from fresh and canned beef aged from 2 to 15 years contained nearly equal amounts of nitrogen but differed greatly in amounts of ashes. The ash-content was the more the older the cans. 2) The results of analyses of the proteins by the Van SLYKE method showed no remarkable difference each other. The analogy of the chemical composition of those proteins indicates the similarity of the nutritive value of them. This result agrees with that of feeding experiments performed by us long years ago. 3) Acid value, saponification value, ester value, iodine value, acetyl value, Hehner value, and Reichert-Meissl value were examined in the fats obtained from fresh and canned beef of different ages of storage, but no definite conclusions were obtained, except that the longer the time of storage the higher was the acid value. 4) Carr-Price test for vitamin A was negative in all of the fats exmnined. 5) The nutritive value of the meat powders obtained from canned beef from 2 to 15 years old, and from canned crab from 1 to 5 years old showed only slight differences, when feeding experiments were performed with albino rats. 6) When the great excess of iron and tin in the form of their chlorides was administrated to the rats, the injurious action of iron was greater than that of tin.