208 THE PRESERVATION OF MILK. 



127. The Content of Pathogenic Germs in Various 

 Dairy Products. 



A few words must be devoted to the description of the treat- 

 ment of skim-milk in the factories of Dairy Associations. As is 

 well known, a large portion of the fresh milk sent to the dairy is 

 not sold as such, but is employed for butter-making. The skim- 

 milk formed in large quantities during this process is, in many 

 instances, partly sold per se, and partly worked up into semi-fat 

 and skim-cheese, milk-bread, and the like. In other cases, the 

 contracts made with the members of the association stipulate that 

 each shall have returned to him, for feeding purposes, a quantity 

 of skim-milk proportional to his deliveries of new. Now, since in 

 these large dairies the cream is removed from the milk by means 

 of the centrifugal machine, it follows that the milk from all sources 

 becomes intimately mixed up together, and consequently if any 

 one parcel of the milk is contaminated, the whole of the skim-milk 

 will become infected thereby. In this manner an epidemic hitherto 

 confined to a single farm may, by means of the returned skim- 

 milk, be rapidly disseminated to all the other cowkeepers. This 

 has actually been frequently proved in respect of the foot-and- 

 mouth disease. In this connection there is an increase in the 

 number of supporters of legislative action in favour of a compulsory 

 heating of the skim-milk returned by dairies to the farmers. As 

 reported by P. VIETH (I.), a Ministerial ordinance has been in 

 force in Prussia since 1894, prescribing that the skim-milk from 

 cows suffering from infectious diseases shall be either kept at a 

 temperature of 90 C. for at least a quarter of an hour, or be heated 

 up to 100 C. before being allowed to leave the dairy. 



It is imperatively necessary that the cream destined for butter- 

 making should be freed from pathogenic germs. According to the 

 concordant results of the researches of L. HEIM (IV.), G. GAS- 

 PERINI (II.), and 0. ROTH (I.), the active organisms of cholera, 

 typhus, and tuberculosis present in the butter long retain their 

 vitality and power. Now, a large proportion of the butter made 

 is consumed in a raw state in the form of bread and butter and 

 the like, and if it has been derived from milk or cream infected 

 with pathogenic bacteria, its consumption is attended with great 

 danger. Consequently a reliable preliminary treatment of the 

 cream to ensure the removal of these germs is in the highest 

 degree desirable. That this can be practically accomplished will 

 be shown in Chapter xxiii., which treats of the artificial souring 

 of cream. 



The same requisition should also be imposed in the case of 

 milk designed for cheese-making, but at present this can hardly 

 be effected, because the treatment required for killing the patho- 

 genic germs lessens the suitability of the milk for the purpose in 

 view, and also modifies the flora of the milk to such an extent as 



