'174 Condensed Milk and Milk Powder 



than the steam. If these precautions fail to remedy the trouble, then 

 the entire process is inadequate and either more heat, or longer ex- 

 posure to the same heat is necessary. 



It is obviously imperative that the fresh milk, as it arrives at 

 the factory, be subjected to the most rigid inspection on the plat- 

 form, in order to guard against the processing of unduly contam- 

 inated milk. 



Blown Evaporated Milk (Gaseous Fermentation) 



General Description. — The ends of the cans bulge out very 

 noticeably, frequently so much so that the seams of the cans burst 

 open. This is due to gaseous fermentation causing high pressure in 

 the cans. The pressure is often so great, that upon opening the cans, 

 most of the contents are blown out with tremendous force. In some 

 cases of blown evaporated milk, the contents have an acid odor, 

 pleasant and aromatic. In most instances, however, they give off 

 very foul odors and suggesting hydrogen sulfide, not unlike ag- 

 gravated cases of Timburger cheese. These odors are exceedingly 

 penetrating and difficult to remove from anything they come in con- 

 tact with. 



Causes and Prevention. — The bacteria causing gaseous fer- 

 mentations in evaporated milk usually belong to the anaerobic group 

 of butyric acid species and in most cases, though not always, the 

 putrefactive types prevail, such as Bacillus putrificus, Plectridium 

 novum and Plectridium foetidum, especially the latter, because of its 

 extraordinary power of resistance to heat. Plectridium foetidum is 

 an obligatory anaerobe and it absolutely refuses to grow under 

 aerobic conditions. It is an actively motile, medium-sized organism 

 with flagella and spores. At one end it has an Indian club-like en- 

 largement, in which appears the spore. The bacillus resembles a 

 kettle-drum stick similar to B. tetani. Under strictly anaerobic con- 

 ditions, and incubated at 90 degrees F., it ferments milk in four days. 

 The milk first curdles, then gradually the curd dissolves (digests) 

 completely, leaving a clear yellow liquid, similar in appearance to 

 butter oil. The fermentation is accompanied by the evolution of a 

 penetrating foul odor. This organism survives exposure for 15 

 minutes to 245 degrees F. Its thermal death point lies between 245, 

 and 250 degrees F. 



