PRESERVATION OF MILK AND ITS TREATMENT 89 



outset. Only skimmed milk is adapted for drying, as the milk 

 fat is quickly oxidised owing to the large surface presented by the 

 powder, and thus acquires a highly unpleasant taste. For this 

 reason condensation must still be regarded as the best method for 

 preserving whole milk, at any rate when it is a question of pre- 

 serving it for a long time. 



Preservatives. If it is only a question of preserving the sample 

 for analysis, comparatively large amounts of antiseptics may be 

 used, e.g., copper sulphate, potassium dichromate or formaldehyde 

 (0-1 per cent.), but all such substances must be excluded if the 

 milk is to be used as food for animals or human beings. According 

 to Lazarus 1 3 the following can be added per litre of milk without 

 the taste being affected : 3 grams sodium carbonate or bicarbonate, 

 1 to 2 grams boric acid, 0-75 gram salicylic acid. Soda naturally 

 delays the souring, but not always the coagulation, as the growth 

 of the rennet-forming bacteria is promoted thereby ; it has also a 

 favourable action on the development of the pathogenic bacteria. 

 Boric acid is without effect in the above proportions, while the 

 salicylic acid inhibits the growth of bacteria to some extent 2 . 



Behring has recommended the addition of a slight amount of 

 formaldehyde to milk, 1 to 10,000 parts, to destroy the tubercle 

 bacteria. This is certainly the highest dilution which can have 

 any bactericidal action whatever. 



The only substance which can come into consideration in the 

 present case is hydrogen peroxide, which is decomposed by the 

 catalase of the milk into water and oxygen, the latter having an 

 antiseptic action in the nascent state. The Danish engineer 

 Budde has shown that the decomposition takes place most 

 rapidly at 45 to 50 C., and as several species of bacteria are killed 

 only by heating to these temperatures, the so-called Buddisation 

 consists in treating the milk for several hours (stirring at first) at 

 52 C. with 0-35 part per thousand of hydrogen peroxide ; the 

 bacteria are thus subjected to the simultaneous action of poison 

 and heat. Commercial 3 per cent, hydrogen peroxide cannot be 

 used on account of the poisonous impurities which it contains, and 

 also the fact that it would dilute the milk'with 1 per cent, of water ; 

 pure hydrogen peroxide must be used, which renders the method 

 too costly, especially as all that is achieved is pasteurisation and 

 not sterilisation. Barthel has shown that milk treated by Budde's 

 process no longer gives Starch's reaction 3 . In order to sterilise milk 

 by means of hydrogen peroxide, 1 to 2 parts per thousand must be 



1 " Zeitschrift f. Hygieine," VIII., p. 207. 



2 According to Proks, 2 per cent, of benzole acid has no greater anti- 

 septic action than 1 per cent of salicylic acid. 



3 " Nordisk Maelkeritidende," 1903, No. 5. 



