METHODS FOR THE ESTIMATION OF 
THe PROTEOLYTIC COM PO WINIS ee 
TAINED IN CHEESE AND MILK.* 
L. L. VAN SLYKE AND E. B. Harv. 
INTRODUCTION. 
When milk-casein and its salts, or paracasein in cheese and 
its salts, are acted upon by dilute acids or alkalies under cer- 
tain conditions or by enzymes or by micro-organisms, the pro- 
teid bodies are split up, forming a variety of complex cleavage 
products. The extent and intensity of such proteolytic changes 
are measured by the proportions and kinds of the different 
compounds resulting from the decomposition. In the ripening 
process that takes place in cheese, we have an instance of 
extensive proteolysis in the case of the nitrogen compounds 
of the fresh cheese, due probably to the combined action of 
dilute acid, enzymes and micro-organisms. In our study of the 
causes that produce cheese-ripening and of the conditions that 
influence the process, we were, at the start, brought face to 
face with the difficulty involved in the lack of satisfactory 
methods for making quantitative separations and determina- 
tions of the products of cleavage formed. While we have well 
elaborated methods for estimating the amount of casein and 
albumin in fresh milk, these are of little aid in studying the 
products of their decomposition. Little attention has been 
given to the development of methods that are applicable to the 
products occurring in this field. Serious difficulties are in- 
volved in such a study. First, we know at present only in an 
extremely meagre and vague way the chemical constitution of 
milk-casein and its allied compounds. As regards the con- 
stitution of the various compounds formed by the proteolysis 

*A reprint of Bulletin No. 215. 
OO 
