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Page:Popular Science Monthly Volume 58.djvu/159

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MICROBES IN CHEESE-MAKING.
151

their growth is entirely prevented by a thorough salting and washing of the surface. In such cheeses the mold may grow within the mass, but not on the surface. Whichever method is used, however, the cheese is presently removed to the so-called 'cheese cellar' for its proper ripening. These cellars may be cool, damp rooms, or caves, and the flavor of some kinds of cheeses is largely due to the nature of the caves in which the subsequent ripening is carried on. In these cellars there is a constant but not very high temperature, and the atmosphere is generally damp. Since the temperature and the moisture are kept as constant as possible during the whole year, the cheese ripening can continue slowly and indefinitely. To a considerable extent differences in the ripening of soft cheeses are due to the different temperatures of the cheese cellars, and this determines the kind of plant life that shall flourish in this soft, nutritious food.

After the removal to the ripening chambers, a new series of changes begins in the cheese, due to new kinds of plant life. But as yet neither the cheese-maker nor the bacteriologist, who has studied the matter most carefully, can tell us much of the nature of the actual changes which occur during this ripening. When the cheese is placed in the ripening chamber it is certain that the growth of the molds is largely stopped, and it is also certain that here begins a growth of a new class of plants which we call bacteria. This moldy cheese, rendered alkaline by the growth of the molds, furnishes a favorable medium for the growth of different species of bacteria. At high temperatures they would speedily decompose the mass, even to extreme putrefaction, but at the low temperatures of the cheese cellars a complete putrefaction does not occur. Bacteria growth takes place probably in all soft cheeses, and as a result the nature of the cheese is profoundly modified. Numerous new chemical products make their appearance, either as byproducts of decomposition or as actual secretions from the growing bacteria and molds. These new products have strong tastes and odors which, as they slowly develop, gradually produce the characteristic flavor of the ripened cheese. If the ripening continue long enough the decomposition grows too advanced even for the strongest palate. But when the proper ripening has been acquired and the tastes and flavors are of the desired character, the cheese is sent to market, highly flavored by the joint action of the bacteria and molds. It is still soft and moist, and the ripening process continues, so that the cheese will not keep good for a very long time. But while it is in the proper condition it furnishes the educated palate with a flavoring product of great intensity, and most highly relished by the numerous lovers of soft cheeses.

While such is the general method of manufacture of the soft cheeses, it must be recognized that the details of the manufacture differ widely. Differences in the kind of milk used, whether whole milk, skim milk,