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
