256 Agricultural Gazette of N.S.W. [April 3, 1920. 



the deterioration, thereby enabling the couipan}- to renied}' the mutter. 

 Knowing the value of arriving at and locating causes of deterioration by 

 means of bacteriology, a scheme was worked out early last year whereby 

 whatever came in contact with the dairy produce after its arrival at the 

 factory until it was placed on the market, could be systematically examined 

 and the results compared. The general adoption by the New South Wales 

 dairy companies of the practice of pasteurising ci-eam made the initiation of 

 such investigations the more opportune. The object aimed at was twofold : 

 (a) To demonstrate the efficiency of pasteui-isation as carried out at 



certain factories. 

 {b) To demonstrate whether or not the product was recontaminated 

 after pasteurisation, and if so, how the infection took place. 

 The methods followed were veiy similar in all cases and were carried 

 out as follows : — 



1. Samples were taken of the cream on arrival at the factory, after blending in 



bulk. 



2. The same lot of cream, after being neutralised and pasteurised bj' either the 



"flash" ov the "holding" system as it came from the outlet pipe of the 

 " flash " or (in the case of the holding s3-stem) direct from the tank, was again 

 sampled. In both cases these samples were obtained before the cooling process 

 commenced. 



3. In the case of the tiash pasteurisation, the plates were exposed 2h minutes, and 



in one case (Example 1) live minutes to the air over the pipe cooler used first 

 to reduce the temperature of the cream. 



4. Plates were atmospherically exposed for tifteen minutes over the cream-receiving 



and neutralising vat in the case of Example I to demonstrate the extent of 

 infection from the water spray tower ; in other cases this was not done. 



5. Where vats were used for holding cream (after passing over pipe coolers) pending 



churning, the tops of such vats being open, another series of plates Mere 

 exposed to the atmosphere — for 2^ minutes in one case (Example 2) and five 

 minutes in another (Example 1). 



6. The same cream was again sampled as it came from the holding vats to enter 



the churns. 



7. A sample was taken of the water used for cleansing and rinsing the churns and 



utensUs. 



8. A sample was taken of the water used to bring butter to the breaking point and 



thereafter used to wash the butter. 



9. A sample was taken of the batter made from the aforementioned cream as >t 



came from the churn. 



10. Plates were generally atmospherically exposed in the churn room 2i jninutes, 

 but in one case (Example 1) for five minutes, in all cases where the butter (or 

 cream as it gravitated along the duming from vat to churn) was exposed to the 

 air. 



11. A sample of the surface of the butter was taken from a box when packed and 

 ready to be lidded. 



In conjunction with making these bacteriological examinations, the 



produce was graded for quality at all stages, thus : — 



(a) Cream on arrival at factory. 



(6) Cream after treatment when ready to churn. 



(c) Butter soon after being manufactured. 



Some delay occui-red in the earlier stages of the work, but eventually with 



the co-opei-ation of th(> Biologist, Dr. G. P. Dariiell-Smith, another start was 



made early in October, 1919, and the results of the first portions of the 



investigation are now available. 



