« 이전계속 »
centage of fat than that which was noticed in the fresh cheese. This apparent increase, however, may be due to analytical error, since in the fresh cheese the fat becomes entangled with highly insoluble caseous matter and is difficult of extraction, whereas after the ripening of the cheese and degradation and breaking up of the caseous tissues the fat is much more readily extracted. While it is not impossible that fat should be formed by the fermentation of the casein it does not seem that it is probable.
In examinations which were made of fresh and ripened cheese of the variety known as Roquefort there was found in the dry substance of the fresh cheese 40.80 percent of protein and 53.91 percent of fat. In the same cheese after it was quite old there was found in the dry substance 37.78 percent of protein and 56.14 percent of fat. These data serve to bear out the theory that fat is formed from the protein. On the contrary, it must be remembered that in the fermentation of the protein a number of volatile bodies are formed, especially ammonia, and thus the diminution in the percentage of protein is probably due to the loss of volatile bodies, and the increase in the quantity of fat is therefore a relative one, probably, and not absolute. There is no doubt, however, of the fact that the quantity or character of the fat does change considerably during the process of ripening. There is no reason for supposing that the fat alone of all the contents of cheese escapes enzymic action. It is profoundly changed in its character by the fermentations to which it is subjected, and this change, while it unsuits the fat for butter, may probably make it more palatable and desirable in cheese.
Digestibility of Cheese.-Reference has already been made to the fact that in the ripening of cheese the protein of the milk, consisting principally of casein, undergoes certain changes which apparently, at least, increase its digestibility. I use the word "apparent" because the flavor and aromas which are produced in the ripening of a cheese act as condimental substances and thus naturally excite the glands which secrete the digestive enzymes to greater activity. Therefore the increased digestibility may be due in part to the increased activity of the digestive ferments as above described rather than to the changes in the casein itself. It must be admitted, however, that these changes during ripening tend to make the casein more granular, softer, and to convert it into compounds more easily acted upon, and are thus favorable to increased digestibility. Experimental studies have shown that in a well ripened American cheese of the Cheddar type 93 percent of the protein present in the cheese and 95 percent of the fat are digested. Artificial digestion experiments have also shown that the pancreas ferments have much more effect upon cheese digestion than the peptic, showing that the cheese is more acted upon in the small intestines, perhaps, than in the stomach. Attention must also be paid to idiosyncrasies in these cases, as there are many people who find it impossible to digest cheese in any form. The eating of
larger quantities than are necessary also tends to derange the digestive organs. A well ripened cheese, therefore, should be eaten rather as a condimental substance than as an actual food product, though its value as a food is fully attested. ("Farmers' Bulletin," No. 162.)
Effect of Cold Storage on the Curing of Cheese.-Attention has been. called, in the description of different methods of making varieties of cheeses, to the ordinary temperature at which cheeses are cured. In European countries these temperatures are maintained without the use of artificial means. In the United States it is difficult to maintain a very low temperature in summer time without the use of artificial refrigerators. Experimental studies have determined that when the temperature of ripening or storage is reduced to a considerable extent below that usually specified for the standard varieties of cheese the quality of the cheese is superior although the time for storage or ripening is very much prolonged. The artificial curing of cheese has been secured at as low a temperature as 40 degrees. There is also a less loss of weight in cheese cured at this low temperature. A cheese which was cured at 40 degrees when examined by experts scored a mark of 92.4 while the same cheese ripened at 60 degrees scored 95. Another test of a cheese cured at 40 degrees scored 95.7 while the same cheese cured at 50 degrees was marked 94.2 and the cheese cured at 60 degrees 91.7.
Preparations of Casein.-Properly in connection with cheese preparations may be mentioned those products which are of a food value, procured from casein itself. The precipitated casein is prepared for the market by washing, drying, and grinding to a fine powder, and is then sometimes called protein. flour. Sanose is a mixture consisting of about 80 percent of casein and 20 percent of the protein derived from the white of egg. The addition of the white of egg enables the casein to remain in suspension when mixed with water and thus causes the preparation to resemble milk. Casein preparations of this form are practically insoluble in water and, therefore, are not perhaps of the best forms of nitrogenous food for invalids. To avoid this insolubility the casein has been combined with alkalies and the preparations are known as nutrose and eucasein. Plasma is also a preparation of casein with alkalies which are added in sufficient quantities to give 7 percent of ash. These caseinates, as they are sometimes called, that is, combinations of casein with alkalies, are soluble in water and are found to be to a certain extent digestible and nutritive preparations. Casumen and sanatogen are other preparations of casein with alkalies or glycero-phosphate. Wonderful claims are made by manufacturers concerning the digestibility and nutritive properties of these preparations. It is doubtful, however, if they have much greater value, if any, than natural casein in the form of milk or as ripened in cheese. Preparations of this kind usually appeal strongly to those who suffer from digestive disorders and therefore highsounding names, which are given to practically the same preparations, lead the
PREPARATIONS OF CASEIN.
seeker after health often to try the same substance under a dozen different appellations. These remarks are not made for the purpose of decrying in any way the merits which these preparations may have but only to illustrate a very marked tendency on the part of many people to attribute extreme virtues to ordinary food substances which are sold under attractive and sometimes deceptive names and whose properties and virtues are advertised in an expert manner. Because a food substance consists almost wholly of pure protein is no indication whatever of its exceptionally high food value. Protein is only one form of food and a concentrated ration of protein in any of these forms is just as likely to do harm as good. For emergency rations, for economy in transportation, and for certain diseased conditions of the digestive organs these preparations are undoubtedly valuable, but they have little claim upon the general public in a state of health as staple articles of diet. They are much more nutritive than the extracts of beef and other meats which have obtained a vogue wholly out of proportion to their dietetic or medicinal value. ("Foods and Principles of Dietetics," by Robert Hutchinson.)
BARLEY (GENUS Hordeum).
In the United States barley is not used to any extent as human food. It has all the nutritive properties of the common cereals and may be considered as a food product, although its chief use is in the making of fermented beverages which will be described in full in the second volume.
Barley is cultivated chiefly in the northern and western portions of the United States and is similar to the oat in this respect, that when the grain is threshed by the ordinary process the first layer of chaff is not separated, and, therefore, it goes into the market unhulled. There are varieties of naked barley which are not much cultivated. The cultivated varieties (Hordeum sativum Pers.) belong practically to one species, although there are very many different varieties grown.
The character of barley best suited to malting will be discussed in the second volume.
Acreage and Yield of Barley.-The area planted to barley in the United States and other statistical data relating thereto for the year 1906 are as follows:
Weight of 100 kernels,.
Starch and sugar, etc.,..
Composition of a Typical Unhulled Barley. From a comparative study of a number of samples of American barley the following numbers are regarded as typical of the composition of the unhulled barley grown in the United States:
The important points brought out in the above data are that the percentage of fiber in the unhulled barley is less than one-half that of the unhulled. oat, as stated further on, while the percentage of ether extract is only about one-half that of the unhulled oat, and the protein is also decidedly less than in the whole oat.
As has been stated, barley is not very generally used in this country for human food, but is used in this and other countries as an ingredient of soup.
FIG. 22.-BARLEY STARCH. X 200.-(Bureau of Chemistry.)
Protein of Barley. The following protein compounds are found in barley in proportionate weight to the total weight of the seed:
As seen from the above table the most important of the soluble proteins is hordein, which in quantity is almost equal to the insoluble protein of the barley grain. The starch granules of barley are recognized by their distinctive shape and size, as revealed by the microscope. A typical microphotographic view of barley starch is shown in Fig. 22.