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As we all know, bacterial development is essential for cheese ripening. Where milk is Pasteurized before the cheese is made, the bacterial development follows the Pasteurization, thus allowing for the development of any harmful organisms that may contaminate the cheese during this period. In other words, there is a long period, which may vary from one month to a year, during which time bacteria develop in the cheese. The consumer does not derive the entire benefit from such a Pasteurization. The case is different when the cheese is allowed to ripen naturally and the Pasteurization is carried out directly on the cheese which is immediately sold to the consumer.
By this method of directly Pasteurizing the cheese it is possible to blend so as to obtain a product of more uniform flavor and texture. The manufacturer of Pasteurized cheese can also obtain an article that is much better adapted for market purposes because the keeping qualities of the product have been considerably lengthened. A few examples of this will be sufficient to demonstrate this point. Incubation tests have been carried out on Pasteurized and un-Pasteurized cheese.
This was done as follows. Ten daisy cheeses were taken and small blocks cut about 3 inches wide, 3 inches high, and 12 inches long. These were wrapped in tinfoil, placed in wooden boxes, and covers nailed on. The remainder of the cheese was cleaned and Pasteurized at 145° F., then run into smaller boxes lined with foil to prevent outside contamination. The 20 boxes were placed in an incubator at 37° C. At the end of 20 days, these boxes were examined. All of the un-Pasteurized cheese, excluding one, were swelled and spongy in texture; the Pasteurized cheese were all in perfect condition, with firm body.
The direct Pasteurization of cheese will also be a great step by way of centralizing the cheese industry. The conditions prevalent in the State of Wisconsin to-day, where cheese is manufactured in 2,700 separate factories, are not conducive to the development of a uniform product, whereas a few Pasteurizing factories properly located in such an area could blend the cheese obtained from a large number of these smaller factories and so standardize this product to a great degree. Anyone familiar with the cheese industry knows that lack of uniformity is one of the main reasons why we have so much difficulty in increasing the consumption of cheese in the United States.
METHODS OF PREPARATION. There are different methods of preparation in use in the United States to-day, Essentially it consists of grinding the cheese, heating in a jacketed container with agitation, and filling into the proper containers, either directly or with specially designed machinery.
CHEMICAL AND PHYSICAL PRINCIPLES INVOLVED.
During this reheating process conditions are favorable for emulsification. Approximately 38 per cent water, 33 per cent butterfat, and large amounts of colloid material in the form of casein and small amounts of albumen are present. The casein is ordinarily very slightly soluble in water, but in the presence of Na and NH. salts it becomes soluble and would therefore promote an emulsion in which the water would be the continuous phase. The plasticity
of the casein is most important because it acts as the cementing agent for all the other ingredients. Not all casein and paracasein 'bodies are plastic, and neither is the paracasein in cheese always plastic. This depends on the method of manufacture, degree of ripening, and acid development in the cheese.
When the cheese is heated there is at first a slight separation of butterfat, so that the cheese particles appear oily. With more heat the cheese becomes plastic or stringy; forming a continuous phase which gradually entangles the other cheese ingredients, making a homogeneous mass. At this stage the cheese is said to "pull up.' This is called the “plastic” state. Upon further agitation the plastic condition is gradually “broken down” and a homogeneous mass resembling very heavy cream results, which has only slight plastic properties.
The length of time that the cheese will remain in the plastic state on heating depends on several factors, such as degree of ripening, variety of cheese, acid content of the cheese, etc. Swiss cheese will usually retain this plasticity longer than American cheese. The cheese may remain in this plastic state anywhere from a few minutes to several hours. Once this plastic condition has broken down it is very difficult, if not impossible, to bring it back again.
The creamy homogeneous cheese, which is the last stage under the heating process here described, has the casein and the fat very intimately mixed, and here we probably have a condition where the oil particles are covered with a very fine layer of colloidal casein, which makes it very difficult to remove the fat from this cheese by ordinary methods. For instance, when this cheese is heated in an oven at 100° C. the fat, although it has a melting point of 37° C., does not flow free from the casein. Such a cheese is not very suitable for toasting purposes in the home. On the other hand, the fact that the casein surrounds the fat so intimately, and also since some of this fat exists in the emulsified form, this cheese should be more easily digested in the stomach than our ordinary cheese. This is a point which would bear further investigation.
BLENDING OF CHEESE.
For best results, cheese having the desired properties must be blended. This is the surest method of getting reliable results. Pasteurization always brings out the defects in the cheese.
To get the best results an examination of the paracasein must be made. Also the character of the finished product desired must be considered.
An analysis is given of a typical cheese that is suitable for Pasteurization:
3. 03 Salt.
.35 Lime (CaO).
3. 35 Acid, 120 c. c. N/10 NaOH per 100 grams of cheese. Formol titration, 58 c. c. N710 NaOH per 100 grams of cheese.
APPLICATION OF PROCESS TO DIFFERENT KINDS OF CHEESE.
The Pasteurization of cheese has a wide application. American Cheddar, Swiss, brick, Limburger, and even Camembert cheese have all been successfully treated. There are several exceptions in the soft cheese group, due to certain complex changes in the casein.
THE EFFECT OF TEMPERATURE AND SALTS.
The temperature is very important and must be watched carefully. Some cheeses can stand more heat than others; for instance, the cheese that has not cured very long and has a tough body will stand a temperature of 150° F. easily, while other cheese slightly weak in body has to be handled more carefully.
Now the question is often asked whether cheese can be heated to such high temperatures without materially affecting the texture and flavor. As for the texture, this has already been discussed, and it has been pointed out that if certain factors are properly watched, a product can be obtained with a very good texture resembling in many ways the original cheese from which it is made. The flavor of the cheese is not materially affected. For instance, it is not very difficult to detect when a Pasteurized product has been made from a wellcured cheese.
Certain salts are important from the standpoints of both effective Pasteurization and proper emulsification. Sodium chloride is of course very effective from the standpoint of killing the bacteria during the heating process, but if too much of it is used it stiffens the product and causes coarseness.
Chairman SAMMIS. The paper is now open for discussion. Are there any questions?
Dr. D. C. CARPENTER (New York State Experiment Station, Geneva, N. Y.). I should like to inquire of Mr. Robinson as to which of the calcium caseinates he holds responsible for the plastic properties of cheese, if any one of them is singled out.
Mr. ROBINSON. We have carried on the work as indicated here, but in greater detail. As far as I can tell, the importance of calcium caseinates there is not very great, and I would not attribute the plasticity to the calcium base.
Doctor CARPENTER. You would attribute it to a perfect casein?
Mr. ROBINSON. Yes; I would. I would say that plasticity is due to certain changes that the casein has to go through and which would probably cause a certain reaction between the casein and certain acids that form during the matting in the curds.
Chairman SAMMIS. Is there any more discussion?
I am happy to announce that our honorary chairman, Doctor Burri, has arrived, and I will ask him to come forward.
(Doctor Burri came forward and occupied a seat on the platform.).
Chairman SAMMIS. The next paper is “Pasteurization of milk for Cheddar cheese making in New Zealand," by Mr. Charles Stevenson, dairy instructor, Department of Agriculture, New Zealand.
Is Mr. Chas. Stevenson in the room? If not, I think I will call upon Mr. J. A. Ruddick, Dominion Dairy and Cold Storage Commissioner, Ottawa, Canada. He is familiar with Pasteurization in New Zealand, as he has made a visit there.
Mr. J. A. RUDDICK. Mr. Chairman, ladies, and gentlemen: I am very glad to say a word or two from the standpoint of a practical cheese maker on this question of Pasteurization of milk in New Zealand. I lived in New Zealand and was chief of the dairy division there some 20 years ago, and revisited the country last winter. I know the character of New Zealand cheese, and having been a cheese maker in my younger days I have kept in close touch with the development of the industry in New Zealand. During the intervening years I have seen a great deal of New Zealand cheese on the markets in the old country.
Some five or six years ago they began this process of Pasteurization of milk for cheese making, and you can understand that it was with very considerable interest that I examined the cheeses when I was there last winter. I tested many hundreds of cheeses in the grading stores and the factories. They are now Pasteurizing about 80 per cent of all milk converted into cheese, and it is their aim to make it universal. It is only a matter of getting equipment. I will describe the equipment first.
They use what is known as a universal Pasteurizer. It is obtained in Denmark, and is of the regenerative type, and, therefore, it is economical to operate. The milk is heated to a temperature of from 160° to 165° F. It is then passed over a cooler, usually a brine cooler, but in some cases a direct expansion cooler. The temperature is reduced to 90° F. as the milk runs into the cheese vats. A starter of about 1} to 2 per cent is added. The cheese makers here will understand that once the milk has been Pasteurized and a starter of uniform character added, the rest is largely routine. You can make a time table for it and set a novice at the work and he can turn out good cheese, and that is, to my mind, one great advantage. The cheeses which I saw in New Zealand were very uniform day after day and week after week. If you compare one factory with another you can not find the difference. So much for uniformity.
Now this is what has been accomplished. In the old days there was a good deal of trouble with a rather dirty flavor in the New Zealand cheese. There are certain times of the year in New Zealand when the milk that is used is not ideal. In the rainy season, the yards and places where the cows are milked get rather deep with mud, with the result that the milk is not always in the best condition. Many producers in New Zealand began without experience as dairymen. They were men from other walks of life, who had taken up a bit of land and begun to practice dairy farming. Now that the milk is Pasteurized the flavor of the cheese is cleaner and the texture silky, and the cheese has the meatiness that is so much in demand on the British markets, instead of that rather stiff, firm cheese that used to be the general standard for Cheddar cheese.
The cheese is of softer texture largely because of more moisture being retained in it. They find they get an average yield of 2 to 3 per cent more cheese from the milk when it is Pasteurized, and it is largely because it retains more moisture. That is an advantage in the markets of the present date; that is the type of cheese that is in demand, a cheese which is meaty and soft, but still firm enough to stand up well. I naturally have been giving a good deal of thought to this matter of Pasteurization of the milk, and I am not convinced that it is a practical question in our country and yours. Even the smaller factories in New Zealand make three or four hundred tons of cheese a year, and that would be a fairly large factory in this country. Nearly all of them have refrigerating plants by which the milk is quickly cooled down to around 90° F. In many factories that would be impossible if they did not have such equipment. I think that is all I have to say. I thank you.
Chairman SamMIS. Is there any question on this subject ?
Dr. A. J. SWAVING (chief inspector of dairying, Holland). Did I understand you to say that all the milk that was used for Cheddar was Pasteurized ?
Mr. RUDDICK. No; I said about 80 per cent of the factories Pasteurize their milk. They have not all adopted it.
Doctor SWAVING. In Holland the whole milk is Pasteurized and then we take 80 per cent milk and add some raw milk. In addition to that we sometimes take wholly Pasteurized milk.
Another question is this: Did you make a chemical analysis of the cheese? It would be most interesting to me to know if the proportions between proteins and fats will change in cheese which is made from Pasteurized milk. I should be glad if somebody could give some information about that, because we have very little data on that matter.
Mr. F. W. Bouska (superintendent, manufacturing, Beatrice Creamery Co., Chicago, Ill.) It appears that the harder cheese can not be manufactured in the warmer climates because of the higher temperature that prevails there.
Mr. RUDDICK. You mean Cheddar, don't you?
Mr. RUDDICK. Of course, you know that New Zealand has not so hot a climate as New York. In New Zealand the climate rarely goes over 85° F. I will tell you this: In Australia where they have a semi-tropical climate the cheese manufacture is developing more than in any portion of Australia. It is not Pasteurized there, though.
Chairman SamMIS. Is there any further discussion? If not we will proceed to the next paper: "The relation of ensilage to cheese making," by Doctor Burri. [Applause.)
Doctor Burri. Ladies and gentlemen: I take this opportunity to voice my appreciation of the honor that has been given to me by my appointment as your honorary chairman. I think the honor has not been bestowed upon me as a man, but upon my country which was the first to go into the investigation of the organisms in cheese.
I trust that my language will not be a serious hindrance for the exchange of our ideas and experiences.
THE RELATION OF ENSILAGE TO CHEESE MAKING.
ROBERT BURRI, Ph. D., director of the Swiss Dairy and Bacteriological
Research Station, Liebefeld, Bern, Switzerland. The preservation of green fodder as ensilage and the manufacturing of cheese have many features that may be studied in parallel. Both concern agricultural products, which at certain