Page:Foods and their adulteration; origin, manufacture, and composition of food products; description of common adulterations, food standards, and national food laws and regulations (IA foodstheiradulte02wile).pdf/247

 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.

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-