CHAPTER V[. 

 MILK TESTING. 



In the early eighties the testing of milk became the most difficult 

 problem which the management of butter and cheese factories had to 

 contend with, and where milk was bought for the city supply or con- 

 densing purposes similar difficulties had to be overcome with the best 

 appliances then available. Milk was paid for during the eighties ac- 

 cording to weight. Therefore, the supplier of rich milk got no more 

 often less than he who brought poor milk. This, of course, was 

 understood from the beginning, but it was those who were extracting 

 the cream and adding water to their milk who were giving all the 

 trouble. 



When the writer was managing the Wanghope Factory (Jamberoo) 

 during the late eighties, the only appliances in practical use were the 

 lactometer and the cream gauges, or creamometers. When these two 

 appliances were carefully used in combination one with the other much 

 good resulted as a means of detecting adulteration. One well prac- 

 tised in the use of the Quevenue lactometer and the conditions of the 

 cream on the creamometer is not easily deceived in milk. But some- 

 thing more was demanded, when purchasing an article of commercial 

 value such as cream, which is valued according to its butter-fat con 

 tents, as was the case at butter and cheese factories. 



The first appliance worthy of notice to grapple with this problem 

 was the oil test churn. The samples of cream were taken in tubes, 

 which were afterwards placed in a frame and agitated until the fat 

 was drawn together in a solid mass ; the tubes were then immersed 

 in warm water until the >iat melted. The proportion of melted fat so 

 obtained was taken as the measure of the butter value of the cream. 



Following on the oil test churn came Marchand's lactobutyrometer. 

 It may be described as a chemical and mechanical appliance, inasmuch 

 as acetic acid and ether were mixed with the milk or cream sample 

 before it was revolved in a frame containing hot water. The lacto- 

 butyrometer was introduced into New South Wales by the Fresh Food 

 and Ice Company. 



Later on we had the De Laval lactocrite and Soxhlet's method, both 

 of which may be termed chemical and mechanical appliances, but as 

 the year 1888 brought forth a host of milk and cream testers o-f more 

 or less merit working on the centrifugal system all of which were 

 superseded by Dr. Babcock's invention it is unnecessary to go into 

 further details of their systems beyond stating that no matter which 

 of the systems may be adopted, honesty oi purpose must be the sole 

 guide of those whose duty it is to take samples of either milk or cream 

 for testing purposes. 



The chemical analysis of milk or cream is neither complicated nor 

 difficult. A small platina dish is accurately weighed and the weight 

 noted. Into it is now introduced an average sample of milk or cream, 

 and the dish and its contents weighed. By subtracting the weight of 

 the dish 'trom the weight of both, the weight of the sample is found. 

 The dish is placed over a burner until all the water is dried off, 

 leaving a residue. It is this residue which passes under the name of 

 " solids." A last weighing of the dish with the milk or cream residue, 

 less the weight of the dish, gives the weight of the solids, and by a 

 single calculation the percentage is found. 



The solids of cream vary according to the method of separation; 

 on the other hand the solids have been .found by innumerable analysis 

 to average about 13 per cent., and while the fat varies in the milk 

 from different cows, the solids left after extracting the fat are a very 

 constant quantity, hardly ever falling below 9 per cent. This gives 

 the chemist a positive basis for his calculations, and enables him to 



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