8 July, 1907.] Overrun in Butter Factories. 399 



undertook instructional work among the factories, and, in addition, a 

 large correspondence involving nearly 20,000 communications was de- 

 spatched during the vear. In each case the instructors reported an im- 

 provement in qualitv before they left the factories ; if their recommenda- 

 tions are followed this will be maintained. It goes without saying that 

 with six months' experience in grading, officers are better qualified to act 

 as instructors on the one hand, and with six months' experience as in- 

 structors they are still better fitted to again carry on the duties of graders 

 on the other. 



Certain experimental work has al".5o been carried out, particularly in 

 the pasteurization of home-separator cream and the use of pure cultures 

 during the season, with, in most instances satisfactory results. These 

 were provided, through the Government Cool Stores, by the University 

 and an extension of the system of pasteurization and the use of cultures 

 is certain. As various officers of the Department will be giving papers 

 on the above and other subjects during the Conference, the subject need 

 not be now enlar<red uDon. 



OVERRUN IN BUTTER FACTORIES.* 



R. T . Archer, Dairy Expert. 



This is a question exercising the minds of those connected with the 

 dairying industry at the present time, and when not properly understood 

 is liable to cause considerable misunderstanding and friction among factory 

 authorities, as it is upon the percentage of overrun that the comparative 

 value of commercial butter and butter fat is based. Take 100 lbs. of 

 butter ; on analysis we find it is composed of 83.3 per cent, fat and 

 16.7 per cent, contents other than fat, which is called the overrun. Then 

 if 83.3 lbs. of fat give 100 lbs. of commercial butter, how much com- 

 mercial butter would 100 lbs. of fat give? 



83.3 : 100 : : 100 =: 120. 



This gives 20 lbs. of overrun for every 100 lbs. of fat or 20 per cent, 

 overrun. The amount of butter fat is correctly given by the Babcock 

 tester as 100 lbs. ; then, if we can save all the fat, convert it into com- 

 mercial butter and sell it, we should get returns for 120 lbs. commercial 

 butter. This is the theoretical aspect of the case. Now for the prac- 

 tical, which is not so simple. 



The overrun is made up of, say, w'ater, 13.7 parts: salt, 2 parts; 

 preservative, .25 part; curd, etc., .75 part; — 16.7. The overrun is 

 a very variable quantity, and is beyond the control of the most skilful 

 manager working under the best possible conditions. This is chiefly due 

 to the variation in the amount of water incorporated in the butter, which 

 is purely mechanical, and exists to the extent of two or three per cent. 

 or more. Taking the analysis of butter exported through the Government 

 Cool Stores for season 1905-6, we find the maximum water contents 16.87 

 and minimum 10.33, average 13.66. For season 1904-5, maximum 16.07, 

 minimum 8.77. In well managed factories we do not find these extremes, 

 but there may, at any time, be a variation of two or three per cent, of 

 water in the butter. 



*Paper read at the Fourteenth Annual Conference of the Australasian Butter 

 Factories Managers" Association, held Mav, I'oy, at Melbourne. 



