BACTERIOLOGICAL TECHNIC. 65 



juices, fruit refuse, etc., which was decomposed or undergoing fermentation 

 or decomposition prior to or at the time of manufacture. The organisms 

 named prevail in varying amounts in different products. Yeast-organisms 

 are apt to predominate in jellies, fruit juices and fruit pulp; bacteria in 

 catsups and pastes; and moulds in certain fruits as strawberries, blackberries 

 and raspberries. 



The presence of numerous dead yeast cells (1,000,000 to 50,000,000 per 

 c.c.) is evidence that the material was undergoing alcoholic fermentation 

 just prior to or at the time of manufacture. Tomato pastes have been found 

 on the market showing over 400,000,000 bacteria per c.c. besides numerous 

 yeast cells and considerable mould. The bacterial content of catsups is 

 apt to run high, from 10,000,000, to 50,000,000 and more per c.c. Not 



m 



Areas 



I sa. mm.. 



Cu.bic Contents 



So*,SW:> 



O.Z.C.mm^. 

 O.ooSC.nim.. 



FIG. 39. Counting apparatus for mould, yeast cells and spores. From the measuring 

 values marked on the slide it is easy to determine the number of mould hyphal clusters, 

 yeast cells and spores per c.c. of the substance under examination. Used with No. 2 

 ocular and No. 3 and No. 5 objectives. 



The rulings are as follows: There are 75 square millimeters in the entire area, of 

 three squares of 25 square millimeters each. The one-millimeter areas are to be used in 

 determining the quantity of mould, dirt, sand and other impurities present. The one- 

 millimeter areas indicated black in the figure are marked off into 1/25 (0.04) square 

 millimeters. These smallest areas are used in making spore and yeast cell counts. The 

 depth is o. 2 millimeter. 



We will suppose that a given fruit sample, as strawberry jam, shows 30 yeast cells 

 in the smallest area (0.2 mm. Xo.o4 mm. =0.008 cm.), then i c.c. of the substance would 

 contain 3,750,000 yeast cells. 



including the vinegar bacteria, which are introduced into catsups and pastes, 

 such high bacterial content is generally due to bacterial development during 

 or after manufacture. The presence of mould organisms and their spores 

 (other than penicillium) indicates the use of mould-infested fruit. Pen- 

 icillium, which is entirely saprophytic in habit, may develop after manu- 

 facture, 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. Exam- 

 ination will show the presence of living yeast cells, or bacteria, perhaps air 

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

 5 



