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temperatures without any apparent loss of its efficacy for cheesemaking purposes. In this medium, using about 1 cubic centimeter of inoculum to 1 liter of broth, an incubation period of from three to seven days at laboratory temperature is required to obtain a heavy growth of the organism. In practice, from 100 to 200 cubic centimeters of this culture to 1,000 pounds of milk has been found sufficient for the proper inoculation of the cheese.

During the past few years the value of the propionic and the bulgaricus starters in factory practice has been amply demonstrated. Cheeses made with these two cultures have won many prizes at scoring exhibitions and fairs. Only a few weeks ago, cheeses made with these cultures won the first six places among the Swiss cheese exhibited at the Ohio State Fair.

THE CONTROL OF OVERSWELLING.

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A frequent difficulty in the manufacture of Emmental cheese in America, and perhaps elsewhere, is a tendency for the cheese to overswell. The cheese so affected usually develops more rapidly than the normal cheese, but sometimes this overswelling occurs in cheeses which have not developed abnormally fast. While defects of this nature are probably due to various causes, very encouraging results have been obtained in their control under certain conditions by the use of another pure culture.

The organism used for this purpose is the organism originally found in cheese by von Freudenreich and named by him B. casei a. As is well known by everyone who has studied the bacteriology of Emmental cheese, this organism develops in large numbers during the curing process, and is the type which is usually found predominating in the well-ripened cheese. It might seem, therefore, that there is nothing to be gained by the inoculation of the milk for cheese making with this organism, but in certain types of overswelling we have found that its use had a marked beneficial effect in the control of this trouble.

On the other hand, we have experienced cases of overswelling in which the use of this culture did not in any degree remedy this undesirable condition. During the past winter this organism was used with most striking results in a factory in California. At the time of its introduction nearly all of the cheeses being made in this particular factory had a tendency to continued swelling after the eye formation had reached the proper stage, and this continued development could not be checked by the removal of cheeses to the cold room. Under these conditions our first attempts at the control of overswelling by the use of Lactobacillus casei were met with marked success; while cheeses in which this culture was not introduced overswelled badly, other cheeses made from the same milk in which this culture was used ceased development entirely when the eye formation had reached the proper stage. Notwithstanding the extremely successful results obtained through the use of the casei starter in this factory during the winter months, during the past summer the results could not be duplicated at all. Although used in the same factory and in the same way in all respects, this organism failed entirely to suppress the tendency of the summer cheeses to overswell.

To sum up our experience with the use of Lactobacillus casei it can only be said that there appear to be conditions under which it may prove to have a distinct value to the manufacturer of Emmental cheese, while under other conditions its use would appear of little if any value. At any rate, this is a problem which merits further study under diversified conditions and in widely separated regions.

Chairman Sammis. Are there any questions?

Doctor ORLA-JENSEN (Denmark). I am very glad to hear that paper of Doctor Sherman, but there are some things mentioned in there that I do not agree with, and which are not used in Europe. It is very interesting for me to hear this paper. I agree that the eyes are produced by the propionic acid bacteria, but I hold that the sweet flavor of the Swiss cheese is caused by one of the lactic acid bacteria.

Doctor SHERMAN. I believe if Doctor Orla-Jensen would try our cultures he would find that they played a very large part in the production of flavor, a very much larger rôle than he now believes.

Chairman SAMMIS. As there are no further questions, we will proceed to Mr. Matheson's paper: “ New developments in the manufacture of Swiss cheese.” [Applause.]

NEW DEVELOPMENTS IN THE MANUFACTURE OF SWISS CHEESE.

KENNETH JESSE MATHESON, research laboratories, Dairy Division, United States

Department of Agriculture.

Domestic Swiss cheese was first made at New Glarus, Wis., in 1854. The annual production at present, including both block and wheel, amounts in round numbers to 20,000,000 pounds, which is nearly all produced by the small cooperative factories in the States of Wisconsin and Ohio. The smaller factories produce from 2 to 4 cheeses daily during the season from April to the end of October. Practically all the small factories receive their milk twice a day, in contrast with the larger factories, which receive their milk but once a day. The smaller factories are provided with curing rooms to hold their output from three to four months, whereas a few of the larger factories are provided with refrigeration and curing space to hold their cheese for a much longer period, with resulting improvement in the quality. Some of the larger factories make cheese during the entire year. There have been several developments in the manufacture of Swiss cheese which may be listed as follows: The standardization of milk, the use of cultures, the centrifuging of milk, and the use of oxygen for suppression of gas.

THE STANDARDIZATION OF MILK.

From June to September there is always more trouble in the smaller factories with glaesler cheese than in any other period of the year. Formerly both culture and nonculture factories resorted to little or no standardization during the summer months, and there were many complaints of glaesler cheese. During the summer months

under our climatic conditions, unless artificial refrigeration is available for the curing rooms, there appears to be danger of glaesler cheese, even though the percentage of fat does not average over 3.1 per cent. In the culture factories there is less loss of fat in whey than in the homemade rennet factories. In the former case the loss usually runs from 0.6 to 0.7 per cent, whereas in the latter case the loss runs to 1 per cent, or higher. It is, therefore, obvious that standardization should be resorted to for the purpose of correcting this difference in whey loss. As has been shown by various investigators, both fat and casein decrease during the summer months, but the casein decreases more in proportion than does the fat. To bring about the proper balance between these constituents it seems advisable to standardize the milk from which the Swiss cheese is made.

In order to guard against glaesler cheese and to arrive at the most desirable relationship between the fat and casein during the summer months, determinations were made upon the milk of a number of factories for these solids. This examination of milk included both culture and nonculture factories. In all cases where cultures were employed the commercial liquid rennet was used, in contrast to the use of homemade rennet alone. The Babcock test was used for fat determinations, and Hart's test for the casein. Samples of milk were taken just prior to the time milk was set with rennet. Cheeses were examined for glaesler condition about the time they were ready to ship. The records of the fat and casein relationship were made on milk during the months of July, August, and September in Ohio.

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The above table gives results of both much and little glaesler quality in the cheese. The bad glaesler cheese would grade as No. 2, whereas the cheese showing little or only a trace were injured hardly enough to change the grading, but they are mentioned in this report, which accounts for the high percentage of glaesler cheese in the table.

Undoubtedly there are other factors that may cause glaesler cheese aside from a low casein-to-fat ratio. On the basis of several years? experience, however, we have found that failure to standardize the milk during the summer months has very often resulted in considerable glaesler cheese.

As a result of this investigation it seems advisable to standardize the milk during the warm summer months in the smaller factories so that it will have 0.72 of a pound of casein for every pound of fat, and with the rennet extract and culture cheese the milk should have 0.8 of a pound of casein for every pound of fat, assuming there is a loss of 0.9 to 1 per cent fat in the whey of the homemade rennet cheese and 0.6 to 0.7 per cent in the whey of the rennet extract and culture cheese.

RESULTS OF USING PURE CULTURES IN SWISS CHEESE MAKING.

Both the bulgaricus and the eye and flavor organisms have been used for pure cultures for several years in our factory at Grove City, which is under Government supervision. Gradually these cultures have been introduced into practically every large factory.

Their introduction into larger factories is somewhat easier, as most of the larger plants employ trained bacteriologists to look after this work. Their introduction into the smaller factories has been somewhat slower, due to the fact that their use here requires more supervision. The cultures are sent either direct from the Dairy Division or from the agricultural college cooperating with the Federal department.

During the last year we have had two men supervising the use of the cultures, and working with a limited number of factories in Wisconsin and Ohio. At present there are about a dozen and a half of the smaller factories growing the cultures. The function of these men is not only to look after the propagation and handling of the starters, but to indicate the manner in which Swiss cheese should be made. Certain modifications in the manufacture and curing processes are necessary when these cultures are employed. Cultures are furnished only to those factories which are selected and which agree to carry out the instructions of the field agent. As a result of several years' experience in the manufacture of Swiss cheese, the improvement by the use of cultures may be summarized as follows: (1) Pure cultures require the use of commercial liquid rennet, which makes results more definite and uniform than where the stomach rennets are used. (2) The use of eye and flavor cultures makes it possible to open up the cheese without difficulty at all times of the year, in contrast with the irregular eye and flavor development for only part of the year found in nonculture factories. (3) Where the Bacillus bulgaricus has been employed we have never experienced any difficulty with the so-called “stinker” cheese, which has always occurred with the nonculture factories. (4) The employment of cultures in the manufacture of Swiss cheese has increased the price for the product as compared with the nonculture factories in the same locality.

THE EFFECT OF CENTRIFUGING MILK FOR THE MANUFACTURE OF SWISS

CHEESE.

Aside from abnormal fermentations, the most common difficulty encountered by the Swiss cheese makers in this country is the overdevelopment of small eyes, or, as commonly expressed, the “over

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setting” of the cheese. While studying the effect of agitation on eye formation in May, 1921, we found that by sending milk through a centrifuge this treatment tended to make fewer and larger eyes and reduced raggedness in eye formation to a minimum. Our first experiments were carried out on a laboratory scale. Later, 21 pairs of regular size Swiss cheeses were made at Grove City, Pa. Each pair of cheeses was made from the same milk, and the same method of manufacture was employed in both cases, with the exception that the milk for one cheese was centrifuged, while that for the other was untreated.

The results of centrifuging the milk for 21 cheeses were 16 fancy, 1 No. 1, and 4 niszlers, while the noncentrifuged milk gave 8 fancy änd 13 No. 1. The percentage distribution was:

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The nature of the experiments necessitated the holding of milk for a considerable period of time, and thereby increased the tendency toward development of niszler cheese. The No. 2 cheese were genuine niszlers. That the increase in No. 2 cheese in the factory output was not so great as in the experimental cheese is shown by comparing the separated milk cheese over a period of several months, from December to June, inclusive. The milk for making this cheese was not mixed, as for the experimental cheese. The cheese made during the months of May and June was all sent through the separator, consequently the percentage of No. 2 cheese in the noncentrifugedmilk cheese was likely to be somewhat higher during these months, as the danger of No. 2 cheese is greater during that period. In fact, however, the proportion of the different grades was as follows:

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The figures indicate that the percentage of fancy che se was greatly increased, that of No. 1 was reduced, and that of No. 2 cheese was also somewhat reduced in the centrifuged-milk cheese. The effect of centrifuging upon the quality of Swiss cheese is illustrated in Figures 1, 2, 3, and 4. The first two cheeses were made from centrifuged milk, while the last two were made from uncentrifuged milk. Each pair of cheeses was made from the same milk and the same methods of manufacture were employed in both cases. Centrifuging the milk for Swiss cheese reduces the number of eyes and increases their size.

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