88 



MILK AND ITS HYGIENIC RELATIONS 



He also showed that lactose in alkaline solution at 45-5o C, 

 gives decolorisation in a few minutes, and methylene blue is reduced 

 when milk is boiled for about fifteen minutes, provided the dye is 

 added at boiling temperature or before boiling. 



He therefore considered that the reaction with formalin-methy- 

 lene-blue was different in origin from that with methylene blue 

 alone. 



In effect Smidt's views have been almost universally acknow- 

 ledged to be correct, although a vast amount of labour has been 

 bestowed upon the subject since his paper appeared. 



Following Smidt's work, Seligmann (2, 4) endeavoured to show 

 that both reactions were due to bacteria, but his results as regards 

 the F.M.B. reaction have not been confirmed by subsequent workers. 



Jensen showed that numerous organisms commonly present in 

 milk can produce a direct reductase. He found that really pure 

 milk did not reduce M.B., but only F.M.B. Koning's investiga- 

 tions also showed the same, as did those of Butterberg and 

 Brand. Similar results were also obtained by Oppenheimer and 

 Sommerfeld. The observations of Oppenheimer showed that when 

 milk is fresh and has been carefully collected so as to be free 

 from bacterial contamination, F.M.B. is reduced within fifteen 

 minutes at 50 C. and within seven and a quarter minutes at 70 C. 

 The rate of reduction was found to have no connection with the 

 bacterial content. 



Sommerfeld, Barthel (3, 4, 5) and Schroeter endeavoured to obtain 

 a relationship between the rate of reduction of methylene blue alone 

 and the number of bacteria present. The matter was also dealt 

 with by Jensen, and results have been tabulated by Barthel (5) and 

 are given below. No relationship is shown between the reduction 

 time and the bacteria present. 



Fred investigated the reducing power of twenty-two strains 

 of bacteria found in milk. Of the twenty-two used, twenty-one 



