April 3, 1920.] 



Agricultural Gazette of N.S.W. 



259 



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 Grams method for microscoj)ic 

 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. 



<H2) Cream before pas 



teurisins 

 (Jl) Cream immediately 



after pasteurising 

 <K1) Cream t w e n t y 



hours after pasleur- 



mng .. 

 <L) Butter in churn 



before salting 

 (Ml) Butter in box after 



packiny; 

 {N) Butter-wash water.. 

 {01) General service 



water (town supply) 



Total 

 Micro- 

 organisms. 



Gelatin 

 Liquetiers 

 and Casein 

 Digest'srs. 



Acid and Acid and , Alkaline 

 Acid Coagu-I Gas \ and 

 lating. j Forniers. Inert. 



Yeasts. I Oidixim 



Moulds. 



102,749,000 

 24,700 



1,296,500 



443,900 



2,244,000 

 329 



2,409 



10,000 



20,000 

 9 



10 



Sample H2 — Cream before Pasteurising. — Before pasteurising, and after 

 thorough mixing in the SOO-gallon- cream-receiving vat, the cream wa'^ 

 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 

 0-6 per cent, of lactic acid. The plates showed the presence of a total of 

 162,749,000 micro-organisms; of these, 1,840,000 were organisms of the 

 Bad. Goli group, or undesirable lactose fermenters, of which three varieties 

 were isolated, viz., Baot. CoU communis, Bad. acidi lactici and Bad. la:tis 



