124 DAIRY BACTERIOLOGY 



the butter is to wash it so thoroughly that the organisms will 

 hardly find any nutrient matter therein 1 . 



THE ABNORMAL FLORA 



As in the case of milk (and, as we shall see later on, of cheese), 

 the normal changes have been dealt with before the abnormal 

 changes, though in the present instance one may note the im- 

 portant difference that while the souring of milk may occasionally 

 be a desired change, the turning rancid of butter is under all 

 circumstances a defect, and if the defects of butter are classified in 

 the same way as those of milk, i.e., into original and secondary 

 defects, most of the latter will be found to be closely connected 

 with the normal process "of turning rancid, although in their first 

 and indeterminate stages they may go under many different 

 names. 



The original butter defects may often be divided into 

 defects in appearance and defects in taste ; they originate in the 

 milk, in the ripening process or in the processes connected with 

 churning, and they may be of a chemical or of a biological nature. 



As the nature of the feed largely influences the melting point 

 of the butter -fat, it has an important bearing on the consistency 

 of the butter., The consistency is also affected by the water 

 percentage and the way in which the water is distributed. It is 

 the fine state of division of the water in the butter which renders 

 the product pliable and easily spread on bread. Storch's re- 

 searches 2 have shown that the water globules in butter should 

 neither be too large nor too small. If they are too small, the 

 butter will be dull in appearance and " thick," and if too large, 

 they will tend to coalesce, giving a wet butter. Normal good butter 

 contains about 3J million water globules per cubic millimetre, 

 while " thick " butter contains about 12 J millions in the same 

 volume. Storch has found that during the souring of cream 

 bacteria may develop, which make the butter thick, but this 

 defect may also be due to causes, chiefly chemical and mechanical, 

 which give rise to a high water percentage. This is especially 

 brought about by churning and working at too high temperatures 3 . 

 If the cream is oversoured the casein may collect in large lumps, 

 which may persist in the butter in cheesy lumps and spoil its 

 appearance and keeping properties. 



1 In Weigmanns work, " Versuche zur Bereitung von Dauerbutter " 

 (" Milch wirtschaftliches Zentralblatt," 1915, p. 353), many valuable hints 

 will be found. 



2 " Forsogslaboratoriets 36 Beretning," 1897. 



3 Qrla Jensen, " Maelkeritidende," 1907, p. 943. 



