686 EXPEEIMENT STATION RECOED. 



Purification of milk by centrifugal separation, C. H. Eckles and S. E. Barnes 

 {loiva Sta. Bui. 59, pp. 55-59). — The results of experiments made at different times 

 during the year to determine to what extent the bacterial content of milk is reduced 

 by centrifugal separation, the distribution of bacteria in the skim milk, cream, and 

 separator slime, and the effect of centrifugal separation upon the keeping qualities 

 of the milk are briefly summarized. In 7 experiments determinations were made of 

 the number of bacteria present in milk before separation and in the mixed skim 

 milk and cream after separation. There was an average reduction of about 36 per 

 cent. At the end of 24 hours milk which had been separated contained on an aver- 

 age 0.03 per cent less acid than nonseparated milk. In 8 other experiments the 

 skim milk contained on an average 29 per cent of the number of germs present in 

 the whole milk, the cream 24 per cent, and the separator slime 47 per cent. It is 

 considered that centrifugal separation removes practically all the solid impurities 

 from milk, but improves the keeping qualities of the milk little if any. 



Sterilization of milk with hydrogen peroxid, Harriette Chick ( Centbl. Bakt. 

 u. Par., 2. Alt., 7 {1901), No. 20, pp. 705-717). — A series of experiments were made 

 on this subject, using a 3 per cent solution of the hydrogen peroxid. It was found 

 that 0.2 per cent of the peroxid was sufficient for the complete sterilization of milk, 

 and that the addition of 0.1 per cent sufficed to keep milk sweet for a week or so. 

 It appeared to make no difference with sterilization whether the milk was freshly 

 drawn or whether it had been allowed to stand some time so that fermentation had 

 commenced. The peroxid, however, imparted a disagreeable, stinging taste to the 

 milk, this being noticeable even in as dilute solutions as 1 part of peroxid to 10,000 

 of milk. The results, therefore, are considered unfavorable to the use of this material 

 in milk for drinking. Small quantities of the superoxid which were decomposed in a 

 short time did not sterilize the milk or preserve it sufficiently for practical purposes. 

 Furthermore, the peroxid seemed to be quite stal)le in milk, especially in weak 

 solutions, the proportion Ijeing a little changed by heating. The material is recom- 

 mended, however, for the preservation of samples of milk for analysis, since it 

 sterilizes the milk completely and causes no change in any of its constituents. For 

 this purpose about 20 cc. of a 10 per cent solution of the peroxid is recommended per 

 liter of milk, which amount is said to preserve the sample indefinitely. 



Further observations upon ropiness in milk and cream, A. R. Ward {New 

 York Cornell Sta. Bui. 195, pjp. 25-39, figs. 2). — The so-called ropy milk from cows 

 affected with garget is pointed out as entirely different in appearance and causation 

 from ropy milk due to Bacillus ladis viscosus. The latter trouble is caused by a species 

 of water bacteria with which the milk becomes infected after it is drawn, and does 

 not make its appearance for 12 hours or more after milking. Referencte is made to 

 an earlier investigation of this subject by the author (E. S. R., 11, p. 282), and addi- 

 tional observations on the conditions under which ropiness occurs and means of 

 prevention are reported. 



In an investigation of an outbreak occurring during the summer of 1899 it was 

 found by experiments that the utensils, the water in the cooling tank, and the dust 

 in the air of infected rooms were means of disseminating the ropy milk bacteria. 

 While the bacteria were not detected in the ice, this is considered as a possible source 

 of contamination, especially as the bacteria show marked toleration toward cold. 



In 1900 another creamery in the locality where the first outbreak was observed in 

 1898 encountered severe trouble from ropy milk. The utensils were thoroughly 

 sterilized, the floor of the milk room was disinfected with a 5 per cent solution of 

 sulphuric acid, and the water tank was disinfected by the addition of 1 oz. of 

 potassium bichromate to each cubic foot of water. This method was effectual in 

 getting rid of the trouble. The conclusion is drawn that with proper cleanliness of 

 utensils, disinfection of the floor, and extra care to prevent contamination by water, 

 ropy milk may be prevented. 



