UNSWEETENED CONDENSED MILK DEFECTS 225 



tion of heat can be facilitated by filling 1 the sterilizer about one- 

 third full of water so that, with every revolution of the frame- 

 work, the cans have to pass through this water once. The water 

 reaches every nook in the interior of the sterilizer, distributing 

 the heat much more uniformly than the steam. If these pre- 

 cautions fail to remedy the trouble, then the entire process is 

 inadequate and either more heat, or longer exposure 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 

 platform, in order to guard against the processing of unduly con- 

 taminated 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 tre- 

 mendous 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 aggravated cases of Limburger 

 cheese. These odors are exceedingly penetrating and difficult to 

 remove from anything they come in contact 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 al- 

 ways, the putrefactive types prevail, such as Bacillus putrificus, 

 Plectridium novum and Plectridium foetidum, especially the lat- 

 ter, 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 enlargement, in w r hich appears the spore. 

 The bacillus resembles a kettle-drum stick similar to B. tetani. 

 Under strictly anaerobic conditions, 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 



