TABLE III
| Correlation Water- and Fat-Content with Ripening | ||||
| Variety of | Per Cent Water | Per Cent Fat | Period Required | Ripening Agent |
Cheese: Soft, | ||||
| Cottage | 70 | trace | a few days | Bacteria |
| Skim Neufchâtel | 70 | trace | a few days | Bacteria |
| Neufchâtel | 50-60 | 12-28 | a few days | Bacteria |
| Camembert | 50 | 22-30 | 3-5 weeks | Molds |
| Cream cheese | 40-50 | 35-45 | a few days | Primarily bacteria |
| Semi-hard: | ||||
| Limburger | 40-45 | 24-30 | 3-6 months | Bacteria |
| Roquefort | 38-40 | 31-34 | 3-6 months | Mold |
| Brick | 37-42 | 31-35 | 3-6 months | Bacteria |
| Hard: | ||||
| Cheddar | 30-39 | 32-36 | 6-12 months | Bacteria |
| Swiss | 31-34 | 28-31 | 9-18 months | Bacteria and yeasts |
| Parmesan | 30-33 | 2-3 years | Bacteria | |
The soft cheeses are quickly perishable products. Bacteria and molds find favorable conditions for growth in products with 45 to 75 per cent of water. If such growth is permitted, enzymic activities follow quickly with resultant changes in appearance, texture, odor and taste. Refrigeration is necessary to transport such cheeses to the consumer, if properly ripened. Trade in these forms may continue throughout the year in cool climates and in places where adequate refrigeration is available. Practically, however, outside the large cities this trade in America is at present limited to the cold months; inside the large cities much reduced quantities of these cheeses continue to be handled through the year.
In the stricter sense, the soft group of cheeses falls naturally into two series: (1) the varieties eaten fresh; and (2) the ripened soft cheeses. Those eaten fresh have a making process which commonly involves the development of a lactic acid flavor by souring, but no ripening is contemplated after the product leaves the maker's hands. In the ripened series, after the making process is completed, the essential flavors and textures are developed by the activity of micro-organisms during ripening periods varying in length but fairly well-defined for each variety.
In contrast to the soft cheeses, the hard kinds are low in water-content, ripen more slowly and may be kept through much longer periods. They retain their form through a wider range of climatic conditions. They develop flavor slowly and correspondingly deteriorate much more slowly. Such cheeses are in marketable condition over longer periods. In their manufacture the cooking of the curd takes a prominent place.
109. Relation of heat to classes.—The close relation between the heat applied and the product sought forms the basis of a striking series of graphs ([Fig. 12,] page 78). These show the changes hour by hour in the heat relation during the making process of a series of widely known forms, each of which is chosen as typical. In some of these forms, heat is applied but once to bring the milk to the renneting temperature typical for the variety. Subsequent manipulations are accompanied by a steady fall in temperature. In other forms, the curd when solid is specially heated or "cooked" to bring about the changes characteristic of the variety. These contrasts are clearly brought out by the graphs which represent practices well recognized for the varieties. The detailed process for these groups is considered in succeeding chapters.