136 MILK AND DAIRY PRODUCTS PART 



sufficiently accurate estimate of the amount of fat present can 

 be obtained. Apart from the fat and water, the other components 

 of butter remain remarkably constant for the same sort of butter. 

 For salted butter made from ripened cream the amount averages 

 about 3 per cent. If the percentage of water in a butter were 

 found to be 13'50, then the fat would be about 83 '5 per cent. 

 if the butter were salted and made from ripened cream. 



In many countries (Germany, England, Switzerland, Holland, 

 and Belgium), laws prescribing the maximum of water and the 

 minimum of fat that is allowable in butter offered for sale are in 

 operation. In Germany not more than 18 per cent, of water is 

 allowed in salted butter, and 16 per cent, in unsalted. The 

 amount of fat must not be less than 80 per cent. In England 

 the standard for water is fixed at 16 per cent. 



The percentage of water in butter is easily and conveniently 

 determined in the following manner. 



About 15 g. pumice stone, which have been ignited and 

 broken into pieces the size of a pea, are put into a flat 

 porcelain dish, with vertical sides, measuring about 6 cm. in 

 diameter. The dish and its contents are dried in the drying 

 oven for half an hour at 100 C., allowed to cool, and then 

 weighed. 



In the meantime, the sample of butter has been melted 

 in water at 40 C., well shaken, and about 5 g. poured over the 

 pumice stone in the dish. The whole must be quickly weighed, 

 then placed in a drying oven for one hour at 100 C., after which 

 the weighing is repeated and the dish returned to the oven. 

 The weighings are made every half-hour until the weight 

 is constant. Generally about two hours are required when 

 working in the above manner. 



The butter must not be dried for longer than three hours, for 

 long-continued heating causes the fat gradually to oxidise, and 

 in consequence the weight of the butter increases. 



A quite constant weight cannot be got, but where the samples 

 are dried for the same length of tim-e at the same temperature 

 good usable results are to be got. ' When it is a question of 

 rapidity rather than of great accuracy, the water may be 

 estimated by the following method, as described by Droop 

 Richmond. 1 



1 Dairy Chemistry, p. 252, 



