CANNED AND CONDENSED MILK 



143 



from the air, it is but reasonable to expect irregularities in the final 

 result unless the invasion of undesirable micro-organisms, which 

 are also present in the air, is carefully guarded against. 



Condensed milk is prepared by concentrating full or skimmed 

 milk. It may be sweetened by adding cane sugar (40 per cent.). 

 While condensed milk contains relatively fewer bacteria than does 

 ordinary milk, due to the process of manufacture, yet none is 

 entirely sterile. The number of bacteria usually present ranges 

 from about 500 or even less to as high as 

 250,000 per cc. Colon bacilli, dysentery 

 bacilli and streptococci are generally 

 absent. Tubercle bacilli have been found. 

 The method for examining condensed milk 

 is much as for ordinary milk, with suitable 

 modifications in making the dilutions. 



Canned condensed milk occasionally 

 spoils, due to the development of bacteria 

 and yeast organisms. Yeast organisms are 

 not likely to appear unless the milk is 

 sweetened with sugar. Spoiling may be- 

 come apparent through the "swelling" of 

 the can. Organoleptic testing is occasion- 

 ally a guide to the condition or quality of 

 the milk. A numerical bacterial limit 

 should be adopted for condensed milk. If 

 more than 1,000,000 bacteria per cc. are 

 present it is not suitable for human consumption. Tubercle bacilli 

 should be absent. According to the limited reports on the subject 

 we may assume that the process of condensing the milk kills all 

 pathogenic bacteria which may be present, including even the more 

 resistant tubercle bacilli. The contaminating bacteria may pro- 

 duce toxins and in marked bacterial invasion it would be well to 

 make inoculation tests with white mice or guinea-pigs, as for toxins 

 in meat and in ice cream. An examination of the centrifugalized 



Fig. 47. — Penicillium 

 of Camembert and Roque- 

 fart cheese. This mold 

 grows at a very low tem- 

 perature. It is closely 

 similar to, if not identical, 

 with P. glaucum. — {Jor- 

 dan after Thorn.) 



