230 BACTERIA IN MILK AND MILK PRODUCTS 



Preservatives are widely used, especially in town milks. They 

 do not, as a rule, kill bacteria in milk, but merely stifle them, and 

 prevent rapid multiplication and increasing acidity. They disguise 

 the true condition of the milk in which they exist. It is to be feared 

 that their systematic addition to milk tends to place a premium on 

 uncleanly and improper dairying. There is evidence, also, to show 

 that by a cumulative process preservatives may be injurious to 

 persons consuming the milk. The most commonly used antiseptics 

 in milk are borax, formalin,* carbonate of soda, and salicylic acid.f 



Secondly, it is possible to remove in part the pollution of milk 

 by filtration. Filtration has been practised for some time by the 

 Copenhagen Dairy Company, by Bolle, of Berlin, and various milk 

 companies. The filters used consist of large cylindrical vessels 

 divided by horizontal perforated diaphragms into five superposed 

 compartments, of which the middle three are filled with fine sand 

 of three sizes. At the bottom is the coarsest sand, and at the top 

 the finest. The milk enters the lowest compartment by a pipe 

 under gravitation pressure, and is forced upwards, and finally is run 

 off into an iced cooler, and from that into the distribution cans. By 

 this means the number of bacteria are reduced to one-third. The 

 difficulty of drying and sterilising enough sand to admit a large 

 turnover of milk is a serious one. This, in conjunction with the 

 belief that filtration removes some of the essential nutritive 

 elements of milk, has caused the process to be but little adopted. 

 Dr Seibert states that if milk be filtered through half an inch of 

 compressed absorbent cotton, seven-eighths of the contained bacteria 

 will be removed, and a second filtration will further reduce the 

 number to one-twentieth. One quart of milk may thus be filtered 

 in fifteen minutes. 



* S. Rideal and A. G. R. Foulerton conclude from a series of experiments that 

 boric acid (1-2000) and formaldehyde (1-50,000) are effective preservatives for milk 

 for a period of twenty-four hours, and that these quantities have no appreciable 

 effect upon digestion or the digestibility of foods preserved by them (Public Health, 

 1899, pp. 554-568). 



f The Departmental Committee on Preservatives and Colouring Matters in Food, 

 1901 (Report, pp. xxiv.-xxv.) recommend: 



1. That the use of Formaldehyde in food and drink is absolutely prohibited, and 

 the Salicylic Acid be not used in greater proportion than one grain per pint or 

 pound respectively for liquid or solid food, its presence in all cases to be declared. 



2. That the use of any preservatives or colouring matter in milk be made an 

 offence under the Sale of Food and Drugs Acts. 



3. That Boric Acid preservatives only be allowed in cream, the amount not to 

 exceed 0'25 per cent., and be notified on a label. 



4. That Boric Acid preservatives only be allowed in butter, the amount not to 

 exceed 0'5 per cent. 



5. That chemical preservatives be prohibited in all dietetic preparations for the 

 use of children and invalids. 



6. That the use of Copper Salts for " greening " be prohibited. 



7. That a Court of Reference be established to supervise the use of preservatives 

 and colouring matters in foods. 



