302 STATE BOARD QF AGRICULTURE. 



milk is standing quiet that the oxygen diminution would be very noticeable for several 

 hours even though fermentation be held in check. The production of carbon dioxide 

 in large amounts by bacteria, the absorption of oxygen or the consumption of oxygen 

 by bacteria have long been known. 



( 'arbon dioxide does not exert any effect upon the germicidal action of fresh milk, 

 >ince it is found that the germicidal action of milk confined without exposure to the 

 air and that which is exposed to the air are practically the same; that is, the ratio 

 of reduction of the number of germs does not differ in the two cases sufficiently to 

 warrant us in drawing any other conclusion. 



When the number of bacteria is estimated before and after the aeration of milk 

 there is no appreciable reduction, consequently, we cannot look upon aeration as 

 directly influencing the number of bacteria. 



It is true that in confined milk germs do not increase as rapidly as in exposed milk 

 but this simply supports the idea that the carbon dioxide or other anaerobic factors 

 exert some influence over the development and increase of bacteria. Without entering 

 into a demonstration of whether the confined conditions or anaerobic conditions of 

 milk are likely to give rise to obnoxious fermentations we have regarded it more 

 feasible to consider only the well established facts already known regarding aerobic 

 and anaerobic conditions as suited to the productions of proper fermentations. Under 

 aerobic conditions usually harmless fermentations take place; that is, fermentations 

 confined to the ternary compounds consisting simply of carbon, hydrogen and oxygen 

 occur, and in the destruction of these ternary compounds as is effected through these 

 fermentations, oxygen must be present in sufficient quantities to yield the desired 

 results. This is not always true, however, but may be regarded as generally true. 

 Of milk fermentations, the ordinary lactic acid fermentation, the fermentation sought, 

 is accelerated by the presence of oxygen, and if such fermentative processes may be 

 facilitated by its action, it follows that harmful fermentations which are capable of 

 development may be held in check. Usually where toxic or harmful effects are obtained 

 the nitrogen molecule is acted upon and broken down. During this destruction toxic 

 substances are formed thus producing the poisonous symptoms when the food is con- 

 sumed. If a review is made of the various cases of poisoning from food, the greater 

 number will be found to result from anaerobic or partially anaerobic nitrogenous 

 decompositions. Brieger has shown that a trace of oxygen is necessary to the pro- 

 duction of poisonous ptomains, but where there is a bountiful supply of oxygen no 

 toxic ptomains are produced. Now, if it is true that the ternary compounds may be 

 decomposed more readily in the presence of oxygen and that by this process the decom- 

 position of the proteids may be held in check the value of substituting oxygen for 

 carbon dioxide is plain. In the case of milk, lactic acid is depended upon to hold in 

 check other fermentations. Repeating, lactic acid fermentation is facilitated by the 

 presence of oxygen, consequently an actual supply of oxygen is required to control 

 the possible detrimental fermentations. Should the milk be practically free from 

 bacteria the need for this control is not so apparently great as where considerable 

 filth has entered the milk, making the possible number of harmful fermentations much 

 greater. 



cm'CLusioxs. 



1. Milk undergoes aeration when exposed to air from the time it leaves the milk- 

 duct of the cow until it is consumed or made into milk-products. 



•1. This aeration is demonstrated by the reduction in the amount of carbon dioxide 

 and the increase in the amount of oxygen. 



3. It has been shown that aerating methods which increase the surface of the milk 

 exposed, facilitate aeration greatly. 



4. Below a certain per cent the elimination of carbon dioxide becomes very difficult. 



5. By this interchange of gases between air and milk, there is a great opportunity 

 offered for the absorption of noxious gases by the milk, unless the interchange takes 

 place in absolutely pure air. 



<>. Agitation of milk favors the interchange of gases, because of the increased 

 surface exposure. 



7. Odor9 and taints resulting from aromatic foods, physiological processes, and 

 disease processes may be greatly reduced permanently. 



8. Odors and taints resulting from bacterial fermentations may be greatly reduced, 

 but they Mill return upon the further development of bacteria. 



