CHEDDAR CHEESE-MAKING 201 



lowed to go beyond 0.16 to 0.19 of 1 per cent acidity in 

 the whey by the acid test or TS to J of an inch of acid 

 on the hot-iron test, before the whey is removed. 



199. Hot-iron test. 1 This test is employed to determine 

 the amount of acid in the curd. A piece of iron, such as 

 an iron pipe two feet long, is heated in the fire to proper 

 temperature. If the iron is too hot it will burn the 

 curd, and if not hot enough the curd will not stick to 

 the iron. When hot, it is taken from the fire and wiped 

 clean with a cloth. A handful of curd is taken from the 

 vat and squeezed dry, either in the hand or in a cloth. 

 This curd is carefully pressed against the hot iron and 

 drawn away. If the iron is at the right temperature and 

 the curd has sufficient acid development, the curd will stick 

 to the iron and when pulled away will form fine threads. 

 The length of these threads determines the amount of 

 acid in the curd. The acid is usually spoken of in 

 terms of the length of threads, as J inch of acid, J 

 inch of acid and the like. The curd must have a 

 slight development of acid before it will stick to the 

 iron. This test takes advantage of the peculiar 

 properties 2 of curd which are produced by the action 

 of the acid on the casein. 



200. Firmness of the ctird. The cheese-maker must 

 be able to judge the firmness of the curd by physical 

 examination. The particles of curd should have shrunken 

 to about one-half their original size and should be of 

 uniform consistency throughout; they should not have 



1 S. M. Babcock, Hot iron test of cheese curd, Wis. Exp. 

 Sta. Kept. 1895, pages 133-134. 



2 Van Slyke, L. L., and E. B. Hart, A study of some of the 

 salts formed by casein and paracasein with acids, their relation 

 to American Cheddar cheese, N. Y. (Geneva) Exp. Sta. Bui. 

 214, 1902. 



