168 REPORT OF THE CHEMIST OF THE 
and diminishing with age of cheese. Various conditions affect 
the amount in new cheese, especially those conditions influencing 
the amount of acid present. 
5. Paracasein, carefully prepared and treated with dilute lactic 
acid, furnishes a product resembling, in both physical and 
chemical properties, the salt-soluble substance extracted from 
cheese. 
6. Paracasein is shown to combine with an acid in at least 
two different proportions, forming two distinct compounds; one 
is the unsaturated or mono-acid salt; the other, the saturated 
or di-acid salt. Such compounds were prepared with lactic, 
acetic, hydrochloric, and sulphuric acids. 
7. Casein forms salts with acids in the same manner as para- 
casein. 
8. The unsaturated salts formed by casein and paracasein with 
acids are soluble in dilute solutions of sodium chloride and in 
50 per ct. hot alcohol, but insoluble in water. The saturated 
“salts are practically insoluble in water, dilute salt-solutions and 
50 per ct. hot alcohol. Both forms are sparingly soluble in 
dilute solutions of calcium lactate and calcium carbonate. 
9. The important changes taking place in cheese-curd during 
the process of cheddar cheese-making, such as the acquired ability 
to form strings on hot iron, the changes in appearance, plasticity 
and texture, and probably the shrinking, are due to the formation 
of the unsaturated paracasein lactate. 
10. The ripening process in normal cheddar cheese, by which 
the insoluble nitrogen-compounds change into soluble forms, be- 
gins, not with paracasein as has been universally held, but with 
unsaturated paracasein lactate. The water-soluble nitrogen in 
cheese generally increases as the unsaturated paracasein lactate 
decreases, and apparently at the expense of the latter compound. 
The first step in the normal ripening process of American cheddar 
cheese is probably a peptic digestion of unsaturated paracasein 
lactate. Some of the facts presented suggest a method of proof 
of the commonly accepted theory of gastric digestion, 
