DAIRY FACTORY PREMISES. 



The cream of milk, whether separated by gravity or by means of the 

 separator, will contain considerably more bacteria per unit volume than the 

 milk. The tiny fat globules passing through the milk serum carry 

 mechanically many bacteria of the milk into the cream, which on arrival 

 at the butter factory and often only a few hours old, is in many cases 

 badly contaminated with bacteria. Experience teaches that such con- 

 tamination can be avoided by efficient pasteurisation (and, if necessary, 

 by neutralisation of excessive acidity) combined with the after-use of a 

 pure culture starter. At the several butter factories visited, all samples 

 were collected with sterile instruments and placed in sterile vessels, and 

 the plating was carried out within half an hour of collecting the samples. 



In the case of example No. 1, an upstairs room in the factory was 

 selected as the most suitable of those available, and although the conditions 

 were not comparable with those of the laboratory, every precaution was 

 taken to prevent undue contamination. The poured plates, with suitable 

 dilutions of the various samples, were kept at 30 deg. Cent, for four days, 

 when counting of the bacterial colonies was commenced, and the organisms 

 were isolated in pure culture and classified according to their action on 

 litmus milk, gelatin, glucose and lactose broth. Smear preparations from 

 the different colonies were stained by Gram's method for microscopic 

 examination. The media used for plating were ordinary agar, glucose 

 agar, litmus lactose agar, an acid agar specially suitable for the develop- 

 ment of moulds, yeast, &c. Samples were also inoculated into peptone water 

 containing bile, salt and glucose, for the ready determination of gas 

 formers. All media were prepared at the Biological Laboratory, Sydney, 

 by Mr. W. J. Reay. Assistance was also given by Mr. W. A. Birmingham 

 in determining mould growths. 



TABLE I. Showing Numbers and Kinds of Micro-organisms found in 1 Gram 

 (1 c.c.) of the following samples. 



Sample H'2 Cream before Pasteurising. Before pasteurising, and afte. 

 thorough mixing in the 300*-gallon cream- receiving vat, the cream was. 

 collected by means of a sterile pipette ; it was received at the butter factory 

 in cans from the surrounding dairy farms, and its acidity was determined at 



