DIRECT EXAMINATION 63 



by molds than are apples, peaches, pears and apricots. Yeasts 

 very rarely appear in the whole fruit, but they develop very 

 rapidly in fruit pulps which contain sugar (natural or added). 

 Yeasts require in addition to sugar, a high percentage of moisture 

 for their active growth, including an ample supply of oxygen (air). 

 The presence in canned fruit products of numerous yeast cells 

 indicates fermentation during the processing. The presence of 

 numerous bacteria in fruit products indicates the use of rotted 

 (bacterially) fruit or bacterial contamination and development 

 during the processing, or both. 



It would appear that most of the bacteria which develop in fruit 

 pulps, especially those from fruits which are quite acid, as for ex- 

 ample tomato pulps, belong to the lactic acid group. Numerous 

 tests in the laboratories of the Bureau of Chemistry show a paral- 

 lelism between the number of bacteria and the amount or per- 

 centage of lactic acid present in tomato catsups. The usual 

 rotting bacteria require more air (oxygen) then is present in the 

 pulp mass and as a result these are soon overgrown by the lactic 

 acid bacilli, if the pulp is allowed to stand for a time without steril- 

 ization. It is, however, very evident that the contamination of 

 such products as catsups, tomato pastes and tomato purees is 

 never wholly limited to lactic acid bacilli. The inclusion of field 

 rotted tomatoes and the rotted pulp material from filthy mixing 

 vats and other parts of the machinery of the unsanitary factories, 

 adds a sufficient number of rotting bacteria to render the article 

 dangerous to health, if consumed. Ravenel and other investiga- 

 tors have shown that when certain food products, as cream and 

 milk, are kept in cold storage, particularly after pasteurization 

 or incomplete sterilization, the development of lactic acid bacilli 

 is checked and the growth of toxin forming bacteria is encouraged, 

 resulting in occasional poisoning , to the consumer. It is very 

 likely that similar conditions may exist in some of the incompletely 

 sterilized canned food products (vegetable as well as animal) which 

 have been stored for some time at a comparatively low temperature. 



