HEAT IN THE PRESERVATION OF FOOD PRODUCTS 46 1 



is properly done the product should be no less attractive to the eye, no 

 less pleasing to the palate, and of no less value from the standpoint of 

 digestibility than the same food when served in the fresh condition. 



Biological Changes. Vital Disorganization. — The entire industry 

 of conservation of foods by means of heat is based on a microbiological 

 process. It is a universally recognized fact that the ordinary spoilage of 

 food is a microbiological change, hence the indiAddual desirous of 

 protecting food from spoilage must give consideration to the microbial 

 agents responsible for the change. 



Normal Flora and Fauna. — ^Aside from a few types of organisms 

 causing disease or specific poisonous conditions, we are unable to desig- 

 nate definite species as those causing canned goods to spoil. Consider- 

 ing the great variety of foods preserved by heat, and the different con- 

 ditions under which they are grown and secured, it naturally follows 

 that the normal flora and fauna of food to be preserved in this manner 

 would embrace a wide variety of species, including some higher fungi, 

 molds, yeasts, bacteria, and low animal forms. Generally speaking, 

 the microbial flora of fruits consists mostly of molds and yeasts, 

 although bacterial forms may also be present. In the case of vege- 

 tables, and of fruits coming in contact with the earth, more species of 

 bacteria are apt to be present, many of them spore formers able to 

 withstand a high temperature. Finally, in meats and fish the living 

 forms may include not only molds, yeasts, and bacteria, but animal 

 forms as well, such as the organisms of taeniasis (tapeworm) and 

 trichinosis. In the preserving industry, therefore, consideration must 

 be given to all these forms, not only from the standpoint of the suc- 

 cessful preservation of the various foods, but also from that of pro- 

 tecting the health of the consumer from possible poisonous substances 

 present or produced in the conserved food, and from possible infection 

 with pathogenic organisms present in the food before it is packed. 



Pasteurization 



Economic Considerations. — In the preservation of food by heat, 

 two processes are applicable, pasteurization, and sterilization. In 

 pasteurization^ the aim is not to effect the permanent preservation of 

 foods or drinks by destroying all life present, but rather to destroy 

 certain species of organisms, thus checking the natural fermentation, 

 and effecting a temporary preservation. 



