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process. Generally Limburger cheese is made from pure milk, but occasionally skimmed or partially skimmed milk is used. The milk is set at rather a high temperature, from 92 to 100 degrees. After the coagulation has taken place the curd is broken into pieces the size of a hen's egg and allowed to settle to the bottom of the kettle as the whey separates. In England a copper kettle is usually employed for the testing vessel. After the whey has separated the curd is taken out and placed in rectangular molds with perforated bottoms, then laid on tables so that the remaining portion of the whey may drain off. The molds are turned from time to time to promote the separation of the whey and to make the cheeses keep their form. The cheeses are next placed in rows on a flat table with thin pieces of boards between them and subjected to light pressure. During this time they are salted by applying salt externally and rubbing the surface at frequent intervals for three or four days. The salt dissolves and permeates the mass. During the salting and pressing the cheeses are kept at a uniform temperature of about 60 degrees. The curing takes place in cellars, well ventilated but very moist, at a temperature of about 60 degrees. As the cheeses ripen they grow soft. The curd takes on its characteristic greasy appearance at the time of the ripening, becoming, at first, a yellow and then a reddish yellow. The softening begins on the outside and proceeds toward the center and the cheese is considered to be marketable when one-fourth of it has taken on its characteristic texture. The softening of Limburger cheese is due to a ferment which breaks down into a soft mass the casein or paracasein of which the cheese is largely composed. By using the same kind of ferments and by following the same process, imitations of Limburger cheese are made in the United States and other countries. These imitations, however, never equal the original in the character of the product nor in flavor or taste, and should not bear the name of the real article.
Limburger cheese was first made in the Province of Lüttick in Belgium. It has, however, come to be considered chiefly as of German production. The chief cause of the putrefactive fermentation which takes place in Limburger cheese is the extremely moist condition in which it is kept. For this purpose the atmosphere of the ripening cellar should be almost saturated with aqueous vapor, containing at least 95 percent of its maximum degree. of saturation. This moist atmosphere, together with the low temperature at which the curing takes place, keeps the cheese soft and promotes the putrifactive ferments. Under these conditions the surface soon begins to get
shiny and soft and changes from white to a reddish yellow. This change makes its way to the center, converting the harsh curd to a soft condition. The time required for this softening of the cheese is from four to six weeks. ("Cheese Making," by John W. Decker.)
Edam Cheese.-Edam cheese is one of the most famous of the cheeses of Holland. It is made at the town of Edam, situated on the Zuyder Zee, about twelve miles northeast of Amsterdam. The milk from which Edam cheese is made should be properly acidified as has already been described. The coagulation takes place and the curd is separated much in the same manner as is used in the manufacture of Cheddar cheese. The curd is held for a time in the vat in a granular condition in order to develop greater acidity and until it will string one-half inch or one inch on the hot iron already described. It is then ready for the mold. The molds are of such a character as to give the cheese a spherical shape about six inches in diameter. Each cheese weighs about four pounds. It has a perfectly solid texture and its flavor is something like that of old Cheddar, except that it is a little more salty and somewhat harder. It is cured at a temperature of about 60 degrees and at a humidity of about 80 degrees. The curing period is somewhat longer than for most cheeses, lasting about eight or ten months and even a year. A slow curing is particularly necessary in the production of Edam cheese.
Coating with Paraffine. In the curing of cheese sometimes it is coated with paraffine to avoid loss of weight. Coating with paraffine does not necessarily interfere with the character of the cheese, though it is probable that it must interfere in some way with the normal ferments. Paraffine is wholly indigestible and may produce injurious effects if swallowed with the cheese. ("Farmers' Bulletins," Nos. 186-190.)
Fancy Cheeses.-There is a large number of cheeses made in which cream enters as a prominent part. It is difficult to give these any particular name and the term "fancy cheese" has been applied to this form of cheese as a whole. They are usually put up in small packages or little pots and thus form an article of diet quite distinct from the large press cheese of commerce. In fact they are intended more for condimental purposes and to be eaten in something of the same manner as butter rather than cheese. These cheeses usually are sold for a much higher price and, therefore, can be regarded more as a luxury than as a regular article of diet.
It might be well to mention some of the more particular varieties of these fancy cheeses.
Gruyère. Gruyère is a cheese made in Switzerland, where it is much prized and from where it is sent to the various parts of the world. It is a pressed cheese and is rather of a larger size than the fancy cheeses already described, and it is difficult to say whether or not it should find a place among them. Parmesan.-Parmesan is a variety of cheese made in Italy. It is about
BACTERIAL ACTIVITY IN CHEESE.
the same size as Gruyère and thus has an intermediate place between the large pressed cheeses of commerce and the fancy cheeses above mentioned.
Gorgonzola cheese is a very familiar cheese made in Italy and belongs to the same class as the two preceding ones. It is in one sense a fancy cheese and yet is made in such quantities as to belong rather to the commercial variety.
Bacterial Activity in Cheese.-Modern science has led to the conclusion that the ripening of cheese is due principally to bacterial activity. The changes which take place in the chemical and physical properties of cheese materials, the flavor and aroma which are developed, the production of mould and other growths are marks of the activity of organisms of different character, living and unorganized. Due credit must be given to the enzymic (unorganized) action in these processes and the enzymes are not regarded as living organisms but, on the other hand, as catalytic agents inducing chemical changes similar to those produced in starch by the action of diastase. The peculiar flavors. of cheeses which are found in different kinds have been ascribed in late years almost exclusively to the character of bacterial activity. This assumption is perhaps correct, but it must not be forgotten in this connection that the same species of bacteria, in changed environments, does not always produce the same results. The activities of bacteria are peculiarly sensitive to the environment, such as change of temperature, physical conditions of different kinds, locality, and other factors of a complex nature, making up the total conditions in which the organisms live. For this reason the attempts to produce peculiar cheeses which belong in particular localities in other localities have not been gustatorily even if technically successful. It is true that cheeses may be made of the types mentioned, having some of the general characteristics but lacking that indescribable something which after all gives true character. Just as it is impossible to make a Rhine wine in California or a Bordeaux wine in New York so is it impossible to make a Cheddar cheese in Ohio or a Camembert cheese in Connecticut.
Number of Bacteria. The number of bacteria, per gram, which appear in cheese varies according to the age of the cheese, conditions under which it is made, temperature, etc. The usual number of bacteria in one gram of cheese varies from five hundred thousand to nearly one hundred million (21st Annual Report of the Wisconsin Agricultural Experiment Station).
Ageing does not seem to increase the number of organisms, since it has been found by some observers that the maximum number present in cheese is found at the time it is taken from the press. It is difficult also to properly sample a cheese for the number of bacteria, since they are unequally distributed in different parts thereof, and the trier, by means of which the sample is secured, may show largely differing numbers in different parts of the same cheese. During the process of curing, especially if the curing be at a high temperature,
the number of organisms decreases. At first the decrease is very rapid and then becomes slower as the cheese becomes riper. The decrease in the number of bacteria when the temperature of curing is raised is somewhat contrary to expectations. It has been found that when a cheese is taken from cold storage, say at 24 degrees F., and placed in a temperature of 60 degrees F., the decline in the number of bacteria is always greater than when the cheese is retained at the lower temperature. This may be due to the fact that bacteria which have been developed at a low may lose their vitality at a higher temperature. On the contrary, the development of flavor does not seem to depend upon the number of organisms since the peculiar flavor of cheese is more rapidly developed at the higher temperature, provided it be not too high, although this be attended with a diminution in the number of organisms. Evidently the conditions which favor the metabolic activities of organisms also favor their destruction, since when they have performed their functions they undergo natural disintegration. The character of cheese is such that when it is once formed there is no more opportunity given for a rapid proliferation of the organisms.
It may be found, however, that the development of bacterial life is not the sole or perhaps not the dominant factor in the development of flavors and aromas in cheeses but that this process is due very largely to the enzymic activities obtained from the rennet and which pre-exist in the milk.
Chemical Changes Which Take Place During the Ripening of the Cheese. Loss of Weight.-During the process of ripening of cheese there is considerable loss of weight, amounting to from 15 to 20 percent of the total weight of the fresh product. This loss is due chiefly to the evaporation of water, while in the fermentation which takes place volatile bodies are formed which also escape with the water. For instance, any free gas, either carbon dioxid, hydrogen, or nitrogen, which is produced will escape, likewise any alcohol which is formed will at least partially volatilize. There may be also a slight loss due to mechanical attrition, but that is not of any consequence. Owing to the loss of water some of the constituents which may diminish in actual quantity have their percentages proportionately increased. These changes are illustrated by the following analytical data:
depends upon the temperature
The quantity of water which is lost in part of the store house and the dryness of the air. The loss of water should not be too great, otherwise the cheese would be dry and the ripening process would not go on in a proper manner. In some of the processes which take place
during the ripening of cheese water is formed. If, therefore, there is no loss of weight during the process of ripening, the ripened cheese would have more water than the fresh cheese and this would impair the quality of the product. The loss of a certain part of water, namely, from 15 to 20 percent must be regarded as an advantage in the production of cheese.
Changes in the Protein. The most important chemical changes, from a digestive point of view, which take place in the cheese are those which the protein undergoes. This protein substance consists chiefly of casein and undergoes profound alteration due to enzymic action during the process of ripening. The casein which when dry naturally forms a leathery, tough material changes into a more soluble and softer product, and during this change there are produced aromas and flavors which add much to the value of the cheese for edible purposes.
CHEMICAL CHANGES IN RIPENING OF CHEESE.
The character of the coagulation of the cheese originally has much to do with the general changes which the product undergoes during fermentation. The cheese makers for this reason must pay special attention to the rennet which they employ in the production of the precipitate. One of the most important of the changes which the casein undergoes is that which results in the production of ammonia. This indicates a complete decomposition of the protein substance, at least in part, so that the total amount of protein which is lost as such may reach as high as 25 or 30 percent of that present in the original cheese. There are also produced notable quantities of lucin and other nitrogenous compounds soluble in alcohol. In general it may be said that the changes in the nitrogen constituents of cheese are extremely helpful to digestion. Not only is the protein of ripened cheese more soluble but even the parts which remain unchanged as far as the protein constituent is concerned are so affected by the action of fermentation as to render them more readily subject to the action of the digestive ferments in the alimentary canal. There is a popular superstition that the use of cheese at the end of a meal helps to digest the other food which has given rise to the adage "Cheese, thou mighty elf, digesting all things but thyself." There is a base of scientific truth in this expression since in ripe cheese the enzymes remain still in an active form and when taken into the stomach must necessarily exercise an influence of considerable magnitude upon the process of digestion. The custom, therefore, which is so universal, of finishing a dinner with a bit of cheese is evidently based upon sound physiological as well as gastronomical principles.
Changes in the Fat.-The chemical changes which the fat undergoes in the process of ripening the cheese are also of considerable importance. It is claimed by some authors that additional fat is produced from the casein during the process of ripening, which is the cause of the lardy appearance of some cheeses. Many observers have found in ripened cheese a larger per