study a comparison of the composition of the frozen ample was made with that of the resh meat; there appeared to be no general tendency for the free ammonia, coaguable proteids, or the albumoses to increase or decrease, and hence chemically the products of bacterial growth, if there were any, were inappreciable.

The authors concluded from their results that frozen meats can be held in cold storage under proper conditions for a period of 554 days. or longer.

It must be noted that in the above investigation the fresh samples were not examined chemically until an average of 3.7 days had elapsed after slaughter, and that in comparing the fresh and frozen results they are from material from different animals. In a second paper Richardson and Scherubel have made a study of beef stored at 2° to 4° C.—that is, above freezing-point. Tests were also made to ascertain whether chemical methods could detect any changes due to known bacterial decomposition of meat. It was found that the total nitrogen, the total solids in the coldwater extract, the coaguable proteids, albumoses, meat-bases, and free ammonia all increased.

The experiments with samples kept at 2° to 4° C. were not, on the whole, satisfactory, but showed that decomposition took place.

In 1909 Emmett and Grindley investigated the effect of cold storage on beef and poultry stored twenty-two to forty-three days, and concluded that the slight changes that occurred did not alter the nutritive value of the meat.

In 1911 Houghton found that chicken meat stored for five months at -21° to -14° C. showed certain physical and chemical changes which demonstrated that it is not identical with the fresh material; they also detected the enzymes peroxydase, catalase, protase similar to trypsin, invertase, and a nitrate-reducing enzyme.

From a review of the above work it would appear that, with the exception of the investigations of Wiley and his associates, Richardson and Scherubel, Emmett and Grindley, and of Houghton, either the conditions as to temperature and methods of preparing meats for cold storage do not correspond with those in common usage of refrigeration, or else in most comparable cases the chemical constituents determined and reported are few; and outside of Emmett and Grindley's and Houghton's work no one, as far as can be discerned, has published any results where fresh and frozen meats were all procured from the same animal, and hence, as far as our present knowledge shows, the differences reported could have been still more, less, or of a different nature, and therefore, outside the work of Emmett and Grindley on beef and of Houghton on poultry, the influence of cold storage upon the chemical composition of flesh has not been definitely determined.

Experimental.

A carcase each of lamb and of mutton, weighing respectively 34 lb. and 48 lb., and graded C.M.C. 2 and 7, was chosen by the author immediately after slaughter; each carcase was split, and, from one half of each, portions of the flesh were removed; the excessive fat was trimmed off, and all bone removed; the portions of the resulting lean meat were finely minced to obtain a uniform sample, and then analysed. The remainder of the carcases were placed in cold storage, and similar samples drawn from time to time up to 160 days, when the experiment ceased.

The mothods of analysis used were chosen after careful consideration of the latest literature on the subject; in each determination two or more results were obtained and the average figure recorded.

It was ound necessary to determine what changes occurred in fresh meat held at ordinary temperatures to ascertain the effect of ripening on the chemical composition of the meats, no such data for mutton or lamb having hitherto been recorded. With this in view, portions of the meat from the freshly killed material were held at laboratory temperatures for seven days, and examined periodically. It was also necessary to ascertain what changes took place in the known absence of bacterial interference; for this purpose samples of the freshly killed material were mixed with thymol and chloroform to inhibit the growth of bacteria without interfering with enzyme action. Samples of the material thus prepared were examined periodically up to seven days.

Lastly, it was necessary to know what changes take place as the result of known bacterial decomposition, and, as suggested by Richardson and Scherubel, portions of the freshly killed materials were mixed with a putrefying meat-infusion. These materials were kept for fourteen days at laboratory temperatures, and examined periodically.

The chemical results, in addition to being expressed on the basis of the original meat (Table A of each chemical experiment), are also recalculated to the moisture-, ash-, and fat-free basis (Table B of each chemical experiment), because owing to the impossibility of removing exactly the same amount of adhering fat from the meat, and also because of the variations of the moisture-content (which will be discussed later), the results expressed on the basis of the original meat cannot be directly compared as to the chemical changes which have taken place during cold storage. Therefore, in order to put the data on a fair basis for comparison, all the results of the chemical experiments are recalculated to the moisture-, ash-, and fat-free basis. It is needless to say that the variation in the amount of fat found has no bearing on the present investigation, and the figures are used merely as a basis in calculating the results. The amounts of nitrogen found in the cold-water extract are also recalculated in their relation to the total nitrogen (Table C of each chemical experiment) for the purpose of showing more clearly the changes taking place in the nitrogenous constituents of the meats.

Owing to the influence of enzymic activity in animal tissues, the chemical experiments also included the separation and detection of the common enzymes. The results of this examination are shown in Chemical Experiment No. 5. Determinations of the acidity of the fat, both fresh and cold storage, were made, and are recorded in Chemical Experiment No. 6.

Bacteriological experiments were carried out to determine the presence or absence of bacteria on the surface and the interior of both the fresh and frozen materials, and also to determine the influence of cold storage upon bacterial life. The results are shown in Bacteriological Experiments 1, 2, and 3. An examination of the physical appearance and structure of the frozen meats was also made.

Discussion.

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The above results show the changes in composition of lamb due to putrefaction.

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The above results show the changes in the composition of mutton due to putrefaction.

The Changes due to the Ripening of Meat.

In order to study the effect of the process of ripening upon meat, experiments were carried out to determine the changes occurring during seven days when the meat was held at laboratory temperatures in flasks, the meat being examined at the end of one, two, three, five, and seven days. The results are shown as Chemical Experiment No. 2, Tables A, B, and C.

In the case of lamb we find a progressive increase of the organic extractives and soluble nitrogen, as shown in Table B. These increase from 21.4 per cent, to 26.21 per cent., and from 3.54 per cent, to 4.42 per cent. respectively. From the same table we see that the coaguable proteids decrease from 11.14 per cent, to 8.86 per cent, on the third day, followed by an increase to 12.25 per cent, on the seventh day. The proteoses increase from 1.31 per cent, to 2.62 per cent.; the peptones increase from 0.38 per cent, to 1.31 per cent, and then fall to 0.68 per cent.; the meatbases increase from 4.25 per cent. to 5.57 per cent. on the third day, and then fall to 5.07 per cent, on the seventh day. The amount of ammonia remains fairly constant till the third day, and then increases considerably, and on the seventh day there is 0.360 per cent.

In the main, similar changes take place in the mutton, and it is concluded that certain progressive changes due to the ripening of the meat take place up till the third day, and then, owing to the increase of bacteria, incipient decomposition takes place. This is evidenced by the marked increase of the ammonia, organic extractives, and coaguable proteids, and the decrease of the meat-bases after the third day.

Changes due to bacterial influence were to be expected, as under normal conditions bacterial infection will take place in all meat unless specially guarded against.

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[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]

The above results show the changes in the composition of lamb due to the ripening of meat.

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The above results show the changes in the composition of mutton due to the ripening of meat.

The Changes due to the Ripening of Meat in the Absence of Bacterial Interference.

In Chemical Experiment No. 3 portions of the minced meat were treated with a mixture of thymol and chloroform to inhibit bacterial action, and the changes due to the ripening of meat allowed to proceed in the known absence of bacterial interference. (Bacteriological Experiment No. 2 shows this.)

Referring to Chemical Experiment No. 3, Tables A, B, and C, we find in the case of the lamb that there is a progressive increase of the organic extractives for three days (see Table B) from 21.4 per cent, to 23.35 per cent., then a drop to 23.10 per cent, and an increase to 23.50 per cent. The total soluble nitrogen increases from 3.54 per cent, to 3.86 per cent, on the fifth day, and then falls to 3.82 per cent. Throughout the experiment changes occur which reach a maximum between the third and fifth days, and the figures remain stationary or slightly revert. It is noted especially that the amounts of ammonia remain about the same throughout, there being no increase which can be attributed to bacterial influence. Similar results are found in the case of the mutton.

It is therefore concluded that during the ripening of meat, in the absence of bacterial infection, changes involving the increase of the organic extractives, soluble nitrogen, meat-bases, proteoses, and peptones, and a decrease of the coaguable proteids, take place to between the third and fifth days, and then further changes cease.

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[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]

The above results show the changes in the composition of lamb due o the ripening of meat in the absence of bacterial interference.

[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]

The above results show the changes in the composition of mutton due to the ripening of meat in the absence of bacterial interference.

The Changes occurring during Cold Storage.

With the previously recorded data regarding the putrefaction of and ripening of meats, it is now possible to consider the nature of the changes

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The above results show the changes in the composition of lamb occurring during cold storage.

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The above results show the changes in the composition of mutton occurring during cold storage.

Chemical Experiment No. 5.—For Detection of Enzymes.

Dr. Rideal, in a paper before the first Refrigeration Congress, suggests that the tenderness and maturing of cold-storage meats are due to the gradual and limited work of natural enzymes, such as pepsin and trypsin, present in the flesh, which cause a certain amount of predigestion similar to that occurring when fresh meats are kept or “hung.” In the chemical experiments under review the enzymes detected were peroxydase, catalase, and an enzyme similar to trypsin, a protase. These were found in both the mutton and lamb from 0 to 160 days in cold storage, and were also found in the thymol- and chloroform-treated material.

Negative results were found in testing for invertase, lipase, and diastase.

Importance is attached to these results, for while enzyme activity goes on slowly at low temperatures, yet the action is not prevented by cold, and undoubtedly the changes found in cold-storage meats are due to the action of the enzymes, especially the trypsin-like protase. The experiments are recorded as Chemical Experiment No. 5.

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Chemical Experiment No. 6.—To determine the Acidity of the Fat.

The development of acidity in fat is a delicate indication of the decomposition of flesh, and one that can be observed long before the senses can detect any alteration. Applying this test to the fat of the mutton and lamb, we find from the results shown in Chemical Experiment No. 6 that no material rise in the free fatty acidity is observed; consequently we can infer that no decomposition has taken place.

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[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]

Bacteriological Experiments.

It is now recognized that the flesh of healthy animals is free from bacteria, but as soon as death ensues, if no measures are taken to guard against bacterial infection, the flesh becomes a suitable field for bacterial invasion and growth.

As bacteria are almost universally present in the air, it is expected that on the surface of meat there will be found bacteria, and that if the meat is allowed to remain unprotected the bacteria will spread to the interior of the meat.

The method of the experiments was to remove portions of the meat from the surface and the interior, using every precaution to prevent contamination. The portions of meat so removed were dropped into flasks containing sterilized bouillon, which were carefully sealed and incubated at 21°C. for fourteen days. These were examined from time to time, and a note made when growth was found to have occurred. In the event of no growth at the end of fourteen days, the contents of the flask were contaminated artificially to show that bacterial growth was possible.

Bacteriological Experiment No. 1 was carried out with fresh lamb and mutton, to determine how soon the bacteria, which were invariably present on the exterior of the meat, could penetrate to the interior of the meat, which was previously found to be free from bacterial infection. It was found that in from five days in the case of lamb to seven days in the case of mutton bacteria could invade the interior of meat when exposed to ordinary temperatures.

Bacteriological Experiment No. 2 was carried out to verify the absence of bacterial infection in the meat used for Chemical Experiment No. 3, where the ripening of meat was allowed to proceed in the known absence of bacteria. In no case did bacteria develop, although it was shown that after contamination the bouillon was a suitable medium for bacterial development.

Bacteriological Experiment No. 3 was carried out to ascertain whether bacterial growth and invasion of the interior of the meat proceeded during cold storage.

In every case it was found that the surface of the meat, even after 160 days of cold storage, was infected with bacteria, but that the interior was