528 MICROBIOLOGY OF FOODS 



Palatability and Digestibility. It is often contended that canned 

 foods are less palatable than fresh foods of the same kind. This lack 

 of agreeableness to the taste is, however, more seeming than real, and 

 arises largely from the prejudice of the consumer against food conserved 

 in tin cans rather than from any actual change. When the preserving 

 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 food 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 to protect food from spoilage 

 consideration must be given to the microbial agents responsible for 

 the change. 



Normal Flora and Fauna. Unlike some branches of microbiology 

 as medical or dairy, we are unable to designate definite species as those 

 usually identified with the spoilage of canned foods. Considering 

 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 trichi- 

 nosis. Weinzirl, Hunter and Thorn, Sadler, and others, by investiga- 

 tions reported in 1918 and 1919 showed that the bacteria most often 

 present in canned foods were of the B. mesentericus type, and those of 

 the colon group. Weinzirl made bacteriological examinations of 1018 

 samples of canned foods including spoiled goods, experimental under- 

 processed samples, and market samples. "The organisms isolated 

 comprised (a) yeasts, 17 cultures, (b) molds, 29 cultures representing 

 7 genera, and (c) bacteria, 392 cultures representing 38 species of which 

 B. mesentericus (Flugge) was the most prevalent." Hunter and Thorn 



