362 MILK 



(Figs. 168, 169). The coagulum is the result of acid or rennin, or 



Y^ 



Fig. 168. — Curd test. A good curd obtained from milk containing no harmful 

 bacteria but many desirable acid-forming organisms (Russell and Hastings). 







I -. _ 



Fig. 169. — Curd test. The curd obtained from milk contaimng many 

 gas-forming bacteria. The irregular, angular holes are mechanical, due to 

 the imperfect fusion of the pieces of curd (Russell and Hastings). 



of the combined action of both factors. It forms more readily 

 at high temperature than at low temperature (Figs. 170, 171). 



