552 STATE BOARD OF AGRICULTURx^. 



perature of pasteuri/inlioii are alive in the pasteurizetl product, some 

 coinpoiiiid or projierty in the milk or cream lias given them protection. 



rUOTECTIVE INFLUENCE OF MILK. 



The thermal deatli point of a cnltnre of liaff. lactis acidi and of a cul- 

 ture of B. coll were compared in bouillon and in sterile separated miik. 

 The average of twelve determinations establishes the thermal death 

 point in milk 3.5° to 4° C. higher than in bouillon {Bact. lactis acidi No. 

 12, in bouillon 64° C. in milk G8° C. and li. coli No. 3, in bouillon G9.5° 

 C. in milk 72° C.) With the idea of extending this comparison a por- 

 tion of a lot of fresh milk was filled into test tubes, the remainder was 

 separated and tubes filled with the cream (25 percent fat) and with the 

 separated milk. Some separated milk was treated with rennet and the 

 whey filtered and tubed. This gives us four divisions of the same milk, 

 i. e., whole milk, cream, separated milk and whey all of which were 

 sterilized intermittently in flowing steam. In these subdivisions the 

 thermal death point of several milk bacteria were determined. The re- 

 sults which are tabulated in Table IV make it clear that the thermal 

 deatli point of bacteria determined in milk or in cream is higher than 

 that for the same organism determined in bouillon. Whey itself pos- 

 sessed some property which raised the thermal death point from 2° to 4° 

 C. ; separated milk from 4° to 6° C, whole milk about 8° C. and cream 

 from 12° to 14° C. The non-acid producing bacilli Nos. IG and 14a re- 

 ceived the same protection from milk and cream as did the acid pro- 

 ducers. In the light of this observation it is not strange that bacteria 

 in milk and cream whose thermal death j)oint in bouillon is a few degrees 

 below the pasteurization temperature are not killed by pasteurization. 



