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viously been inoculated with the gas-producing organism, used in the above experiment, the development of gas could be either completely checked or nearly so. About 20 cubic feet of oxygen was run into the milk by means of a glass tube to which a perforated copper coil was attached. The temperature of the milk was from 10° to 15o C.
In the check cheese which was not treated with oxygen, difficulty was experienced in getting a niszler effect throughout, though a niszler or pressler tendency would often be in evidence along the edge of the cheese. In some cases the difference between the cheeses from treated and untreated milk was very marked, as is shown in cheeses 3 and 4, 8 and 9, Figures 6 and 7. Cheeses 3 and 8 were treated with oxygen, whereas cheeses 4 and 9 were not treated with oxygen. The two cheeses in each pair were made from the same milk, to which 1,000 cubic centimeters of gas-producing organisms had been added. All the cheeses were made by the same method with the exception that in cheeses 3 and 8 oxygen was added, while in cheeses 4 and 9 no oxygen was added.
In most cases from 300 to 500 pounds of milk were employed in the making of each cheese. In some cases the cheese was cut for examination the day after making; in other cases the cheese was allowed to ripen three or four months before examination, as was the case with the cheese in Figures 6 and 7. The use of oxygen did not injure the flavor of the cheese in any way, nor did it appear to have any appreciable effect upon the setting of the cheese. If there was any change it was slightly in favor of the oxygen treatment. The action of the oxygen as indicated by dilution tests seems to be inhibitory rather than actually destructive of the gas organisms. It seems, however, that the gas-producing organisms are merely held in check, whereas the lactobacilli develop normally.
The commercial possibilities of the oxygen treatment have not been fully tested. We have made a few cheeses on a factory scale, but with no satisfactory checks. Whether or not old milk or milk subject to the niszler fermentation can be utilized by means of this treatment remains a question. It will be necessary to make cheese over a long period from mixed milk, giving suitable checks, before definite conclusions can be drawn. The oxygen treatment, however, has given us the only laboratory results that have offered any hope that this type of anærobic fermentation may be controlled in Swiss cheese.
Chairman Sammis. This has been a very interesting subject, and I think there probably are some questions.
Mr. C. J. MONRAD (Little Fails, N. Y.). What I would like to ask is information regarding the flavoring by ozone.
Mr. MATHESON. We found that it gave us more off flavor probably from the fat, and we did not follow it up much further, but thought we could do just as well by oxygen. We just made a few cheeses by that method, but hope to continue by that treatment, and by using a smaller quantity we might be able to get around the off flavor.
Mr. Geo. E. FERTIG (Deis-Fertig Dairies Co., Dover, Ohio). In the process with oxygen, do you change your temperature! ?
Mr. MATHESON. It is true a lower temperature will hold a higher percentage of oxygen. The milk we were using for our experiments was cooled probably to 13° or 14° C. at the time of using it. I think it is quite possible to use a considerably higher temperature than the temperature that we have used. I do not think there is any question about that, although it would be probably more expensive to use a lower temperature for the introduction of oxygen.
Chairman SamMis. On our program this afternoon there are a number of papers which have been prepared by authors who were not expected to be present. We also have one other paper, " The flora of American commercial Cheddar cheese and its relation to quality," by G. J. Hucker, associate in research, New York State Agricultural Experiment Station, Geneva, N. Y. I hope Doctor Hucker is here, or will send some one to go into this subject.
There is another paper which has just been added to the program by Dr. Masayoshi Sato, professor of Hokkaido Imperial University, at Sapporo, Japan, on the subject “ Mongolian cheese or “Naii Tofu.?" We will perhaps hear from Doctor Sato later on.
' Among the other papers which have been sent in, the audience has its choice as to which one of these should be read and discussed. Among those we have present with us is Dr. G. Koestler, chief, chemical division, Liebefeld Experiment Station, Bern, Switzerland, and the subject of his paper is “ Some milk types characterized by their rennin reaction and their importance in cheese making."
SOME MILK TYPES CHARACTERIZED BY THEIR RENNIN REACTION
AND THEIR IMPORTANCE IN CHEESE MAKING.
G. KOESTLER, Ph. D., chief, chemical division, Swiss Dairy and Bacteriological
Research Station, Liebefeld, Bern, Switzerland.
I would like to describe briefly three different types of milk which do not coagulate with rennet in a desirable manner:
(1) Type A, which is in Switzerland known under the name of Rassalzige” milk (highly salty milk). We know that this kind of milk is caused by more or less severe catarrhal inflammation of the udder glands, and that bacteria can remain a long time in the udder; in the latter case we have generally a chronic inflammation of the udder; the milk obtains a salty taste. For cheese making this kind of milk is very dangerous (causing “ stinker," or putrid cheese).
(2) Type B, which does not coagulate with rennet, seems chemically not changed at all. This kind of milk will be normal when we add a certain amount of good milk. Van Dam has studied this type of milk and he states that this milk has not enough of colloidal calcium (calcium combined with casein, “ caseinate").
(3) Type C has already caused serious trouble in cheese making in Switzerland. This kind of milk coagulates with rennet often at the right time, but the coagulum remains tender or weak during the manufacturing process.
In this case the cheese maker is forced to spend more time in the working of this cheese curd, more than twice as long as with normal milk. For this reason, the cheese does not ripen well because it does not have the proper texture; this can influence the fermentation in an undesirable way. This kind of milk can be found in some dairies in a remarkably great amount. It is more than curious that we find this trouble in the secretion in two generations of cows (mother and daughters). Even 5 per cent of this milk inixed with good milk has a disadvantageous influence on the quality of our Emmental cheese. Recently we have studied six cases of this kind of trouble in cheese making and have found that type C was the real cause of the trouble. It may be said that this type of milk is difficult to detect because the chemical content is practically the same as that of good milk. We can only find out this milk when a rennet test is made, and in this test we must not only look to the time necessary for coagulation but also to the time of matting and the texture of the mat.
In closing I want to draw your attention to the fact that in the State of Wisconsin all the makers of Swiss cheese complain that the milk (especially that from silage-fed cows) will not coagulate in the desired manner. I do not know to what degree this is true, but according to our experiments and knowledge the last type of milk, type C, can be found coming from cows which are in the full period of lactation, and the first-named type of milk, type A, is often secreted by cows which are forced to an exceptionaly high milk production.
Chairman SAMMIS. Is there any discussion of this paper? I am sure it has been of interest to us, and we shall be glad to hear any questions there might be on this subject.
Sir Arnold THEILER. He speaks of the salty milk coming from an udder which is inflamed. Is that right?
Doctor KOESTLER. The milk comes from cows in which the glands of the udder are inflamed.
Sir ARNOLD THEILER. We recognize three distinct types of inflammation of the udder. Do you, perhaps, know which particular type this is?
Doctor KOESTLER. I spoke only of the types of milk which we take for cheese making, but there are other kinds of inflammation where we do not take the milk, but in this particular case the bacteria are settled in the glands of the udder.
Chairman SAMMIS. Is there any further discussion?
I see among the audience several faces of those whom I am sure you would like to hear from. I see Prof. A. Peter, director of the Government Dairy School and professor of dairying in the Federal Technical High School, of Zurich, Switzerland. In addition to that he is a great economist. We will be very glad to hear a few words from Professor Peter. [Applause.]
Prof. A. PETER (Rütti-Zollikofen, Switzerland). Mr. President and gentlemen: I have been quite familiar with this cheese question for 20 years. When I went to the technical school I first worked on the bacteriology and the chemical side of our cheese making. Professor Burri, our honorary chairman, was then my instructor in bacteriology, and I worked with him along that line. Then I became a director of the dairy school and had to organize an inspection of our cheese factories. I had to go out into the cheese factories to see what might be the origin of the different problems the practical cheese maker has to solve in his work. In this work I always noted
that the first condition was to have a sound milk that came from a sound cow with a sound udder. I studied that milk that Doctor Koestler has now become an expert on, the salty milk. I am very familiar with it from the standpoint of a common interest. We wan: the cheese makers of Switzerland to bring in the defective milk.
These inspectors go out among the farmers and look after the cows and tell the farmers what this cow has or what that cow has, and we are very much indebted to Doctor Koestler for the work he has accomplished along that particular line. He now has the factories producing cheese in a good, scientific manner. His work is very important to the practical cheese maker. The inspectors are paid by the dairy organizations. The dairy association pays onethird, the district government is paying one-third, and the department is paying one-third of the cost. These inspectors go out early in the morning before the farmers bring the milk in to see what rennin or culture this cheese maker is using. When the work in the factory is done they go around to the farmers to see if they have healthy cows, if they are feeding the cows properly, if they are milking them properly and if they are handling the milk properly. These inspectors are very good, very important, and their work is indispensable to the cheese maker, and the cheese maker is very glad for the work they are doing. I thank you. [Applause.]
Chairman SamMIS. We will have the pleasure of hearing a brief abstract of the paper that was to have been read by Mr. Hucker.
(Dr. Breed gave a brief abstract of Mr. Hucker's paper.)
Chairman SAMMIS. Are there any of the remaining papers listed for this session that you wish read for the purpose of discussion! They will be read by title.
THE FLORA OF AMERICAN COMMERCIAL CHEDDAR CHEESE AND
ITS RELATION TO QUALITY.
G. J. HUCKER, New York Agricultural Experiment Station, Geneva, N. Y.
It is a well-established fact that the ultimate flavor and quality of cheese are dependent largely upon the action of certain microorganisms which are found living either within the curd or on its surface during the ripening process. Any desired change in the character of the ripened product must be secured either by insuring the introduction of the proper kinds of organisms during the manufacture or ripening, or by such manipulation of the curd or ripening cheese as to allow the desirable flora to gain an ascendency over the large number of miscellaneous inert or undesirable types which may be present.
In the manufacture of many of the so-called soft cheeses a combination of both of these procedures is followed, the desired organisms being added in sufficient numbers to practically overgrow all other types normally occurring in the milk, thus giving the characteristic texture and flavor which may be found, for example, in Camembert, Brie, etc. In all such cases, the type of cheese secured is dependent entirely upon the kind of organism introduced. The work of Thom, Mazé, and many others has made such probedure possible by a study of the kinds of organisms found in the ri pening cheese, with a result that various molds, bacteria, etc., are now known which under certain conditions have the power to produce the desired results.
Similar methods have been followed in the production of highgrade Emmental cheese. In this instance, certain organisms, as studied by Freudenreich, Jensen, Burri, and Sherman, have been found definitely associated with the development of the characteristic flavor which, in this case, is probably closely allied with the production of the so-called eyes. Certain of the lactobacilli and propionic acid organisms have been shown by the above investigators to produce desirable results if properly handled and introduced during the process of manufacture. În certain varieties of Italian cheese (grana) Gorini has found that better grades of cheese are usually associated with a group of acid proteolytic cocci, the action of which upon the curd is responsible for the improved quality of the ripened cheese.
In the case of Cheddar cheese, and the same is true of other varieties, the flora of the ripening curd plays a large rôle in the production of a desirable or undesirable product. The only control upon this flora which has been used in practice has been the addition of lactic acid starters (Strep. lactis) and the curing of the cheese under conditions of temperature, moisture, etc., which have been found by years of practice to give the most desirable results. Following such a procedure, it is evident that the ultimate quality of the ripened product depends largely upon the flora of the milk to be made into cheese. Improvement in the quality of American Cheddar cheese can be brought about either by producing milk which contains as few organisms as possible, the desired flora being added as a starter, or, better, by certain manipulations in the dairy to produce milk which will contain the proper flora for the insurance of Cheddar cheese of a high quality. To follow either of these procedures successfully, more should be known regarding the flora of Cheddar cheese and the relation of such flora to its quality. With such information at hand it becomes necessary to determine which groups of organisms are associated with the better grades of Cheddar cheese and which are characteristic and probably accountable for the large amount of poor-quality cheese found in our local markets.
In previous studies on the flora of American Cheddar cheese, Harding and Prucha, at the New York Agricultural Experiment Station, and Russell, at the Wisconsin Experiment Station, concluded that Bacterium lactis acidi was the predominating organism in the earlier stages of the ripening; while later the Department of Agriculture, at Washington, and the Wisconsin Experiment Station pointed out that, although B. lactis acidi (S. lactis) was present in large numbers in the earlier stages, it is replaced in the later curing by the lactobacilli group which, in the final periods, are the predominating types. In both of these investigations only cheese of high quality was used, as the aim of the investigations was to determine the flora during the ripening of Cheddar cheese of good quality.
Recently the New York Agricultural Experiment Station has again undertaken a general floral study of Cheddar cheese, which covered a wide variety of samples obtained from a number of sources.
* See N. Y. Agr. Exp. Sta. Tech. Bul. No. 90, 1922.