BACTERIOLOGICAL TECHNIC 



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pastes, such high bacterial content is generally due to bacterial develop- 

 ment during or after manufacture. The presence of mold organisms and 

 their spores (other than Penicillium) indicates the use of mold-infested 

 fruit. Penicillium, which is entirely saprophytic in habit, may develop 

 after manufacture, particularly on the surface of inadequately sterilized 

 fruit products in containers not entirely filled. 



"Swelling" of cans containing fruit products is generally due to yeast 

 development, though it may also be due to bacterial activity, and indicates 

 inadequate sterilization of either the container or of the fruit or both. 

 Examination will show the presence of living yeast cells, or bacteria, per- 

 haps air bubbles, and the characteristic vinous odor of yeast may be noted. 



Based upon such conditions as can be made to prevail in carefully oper- 

 ated factories, the following may be given as the limits of the number of 

 organisms permissible in the fruit products under discussion. 



a. Yeast cells, either living or dead, not to exceed 1,000,000 per cc. 



b. Mold spores not to exceed 1,000,000 per cc. 



c. Hyphal clusters and hyphal fragments not to exceed 10,000 per cc.; 

 or not over 25 per cent, of separate and distinct fields of view under the 

 compound microscope should show hyphal clusters or hyphal fragments. 



d. Bacteria (either living or dead but not including vinegar bacteria in 

 products to which vinegar is added )not to exceed 25,000,000 per cc. 



The above figures apply only to fruit products supposedly made from 

 comparatively fresh fruits and fresh fruit juices. The yeast, bacterial and 

 spore counts are made with a Thoma-Zeiss hemacytometer (Turck ruling) 

 using a No. 5 (^ in.) objective with No. 2 (i in.) ocular. 



H. Quantitative and Qualitative Bacteriological Testing.- The following 

 will serve as a general outline of bacteriological analyses which may be made 

 in food and drug laboratories. The substances which require such bac- 

 teriological examination include catsups, tomato pastes, vinegars, water 

 supplies, mineral waters, milk, ice creams, any and all substances which 

 are suspected to be sewage contaminated, etc., etc. 



The sequence of processes here given bear a progressive relationship. 

 Whether process II is carried out will depend upon the findings under I 

 and whether III shall be undertaken will depend upon the findings under II. 

 The essential facts to be ascertained are whether or not there is possible 

 sewage contamination as indicated by the presence of the colon bacillus, 

 sewage streptococci and possibly the typhoid bacillus. The typhoid 

 agglutinating tests are apt to prove unsatisfactory. In most instances 

 this test will be unnecessary as the presence of the colon bacillus is evidence 

 that the food, drug or drink is excessively contaminated with sewage 

 and is hence unfit for human use. 



I. Direct Count. For this purpose the Thoma-Zeiss hemacytometer 



