372 STATE BOARD OF AGRICULTURE. ' 



doubt, from the air, as is the^case with other mold contaminations. In 

 the air of dairies, Oidium lactis is commonly very abundant." 



At the Ontario Agricultural Experiment Station, and in the Dairy Di- 

 vision of the New Zealand Department of Agriculture, opportunity has 

 been given for observing, in a superficial way, the changes wliich take place 

 in butter sent in refrigeration to the English markets. Gray studied the 

 problems of pasteurizing, salting and packing, experimentally. 



Pennington studied the effect of low temperature upon the development 

 of the micro-organisms present in milk, and found an enormous increase 

 even when the milk was kept at a temperature below the freezing point, 

 so that it became partially congealed. 



Rogers excluded air from the butter in tubs by coating the tubs with par- 

 affin. This prevented the growth of molds and favored the keeping of the 

 butter. 



From these investigations and others, cited in Lafar's Handbuch der 

 Technischen Mykologie, II, pp. 210, (H. Weigmann), Reinmann, Unter- 

 suchungeyi ueber die Ursachen des Ranzigwerdens der Butter, and by Otto 

 Rahn, Die Zersetzung der Fette, we may draw the following conclusions: 



The term "rancid" is not definitely fixed. Very probably w^e have dif- 

 ferent chemical compounds in different rancid butters. Free butyric acid 

 certainly causes a rancid taste in butter, but its amount is not always high 

 enough "to cause an off flavor. The same is true of ethyl butyrate. The 

 decomposition of the unsaturated oleic acid is due to oxidation brought 

 about more by the action of light than by organisms and causes not so much 

 a rancid as a tallo^^y taste. The rancidity of butter is almost certainly 

 due to micro-organisms, some of which effect a hydrolytic decomposition of 

 the glycerides of the saturated fatty acids, for butter sterilized by heat 

 keeps indefinitely if kept from micro-organisms, light and air. It cannot 

 be due to a fat splitting enzyme originally present in the milk because if 

 so, the butter from pasteurized or sterilized cream should keep, whereas 

 it spoils in the same way as ordinary butter, though usually much more 

 slowly. However, most of the bacteria found in butter do not seem to have 

 any relation to rancidity, though some of them do cause an alteration in 

 the taste. From the investigations of Hanus and Stocky we know that 

 several molds, especially Penicillium glaucum, Aspergillus, and also Mucor, 

 decompose fat into free acids and might cause a rancid taste in this way. 



All investigations show that the spoiling of butter is an aerobic process, 

 beginning at the surface and slowly penetrating through the who'e butter. 

 A number of instances are on record of the finding of butter which had 

 evidently been buried in bog water for centuries, in one case a sample of 

 about 20 pounds having been submitted to the ordinary chemical determi- 

 nations after its recovery. That under these conditions decomposition 

 would take place very slowly indeed, is not surprising, since these fatty 

 acids consisting of long chains of CH ^ groups and only two oxygen atoms, 

 are very difficultly decomposed by any anaerobic process. The glycerine 

 may, of course, be decomposed ailaerobically, but this constitutes only about 

 five per cent of the total fat. 



These results refer to butter kept at ordinary temperature, and would 

 naturally differ from those obtained in cold storage. 



