724 EXPERIMENT STATION RECORD. 



does not appear as rich as it really is. It lias been suggested tliat it 

 may be due to the fat globules of the milk and cream being split up by 

 tbe digestion and beat ; and consequently the influence of heat on the fat 

 globules and the viscosity of the milk and cream was studied. Whole 

 milk, cream, skim milk, and whey were used, the number and size of 

 the fat globules, the viscosity, and the specific gravity being deter- 

 mined in the samples before ])asteurizing, after pasteurizing, and after 

 subsequent sterilization. In some cases the efl'ect of heating at a lower 

 temperature than that for pasteurizing and the effect of beating with 

 an egg beater were also studied. The data for these observations are 

 fully tabulated. 



"All determinations of viscosity in pasteurized or sterilized milk or cream have 

 shown a decided influence of heat on the viscosity coi-fficient, the viscosity heiug 

 lowest in every case where the products were subjected to a temperature of 65*^ or 

 above; this influence is noticeable almost as distinctly in the outward physical 

 appearance of the cream as shown by the viscometer tests; cream which would have 

 the appearance of being very thick before being warmed appears to be of only 

 average thickness after having been heated, flowing readily from one vessel to 

 another. . . . 



"The A'iscosity of the milk was not affected by the application of heat under 30- C, 

 but there was a distinct decrease in viscosity, at 30"^ and still more at 35^, as is shown 

 in case of sample B, where sufficient acid had not yet been developed to cause an 

 increase in the viscosity. The changes in the physical properties of cream (and 

 presumably also of milk) brought about by the ai)plication of heat therefore occur 

 even at temperatures below that of the melting point of butter fat. . . , 



"The influence of pasteurization [of centrifugal skim milk] is shown in a uniformly 

 lower viscosity in the pasteurized samples; subsequent sterilization, on the other 

 hand, is seen to increase the viscosity, possibly on account of coagulation of the 

 milk albumen; while the results obtained after the first and the second sterilization 

 are jn-actically the same, there is an increase after third sterilization, with stationary 

 results after this determination. . . . 



"The increase in viscosity [of whey] both in the pasteurized and the sterilized 

 samples in this case must be attributed to the precipitation of albumen ; this takes 

 place partly, in a very finely divided state, in heating the sweet whey to 65'^ C, but 

 at sterilization the precipitation is apparently complete, a heavy white flocculent 

 precipitate being formed which greatly interferes with the rotation of the viscom- 

 eter cylinder. Any influence that the heat may exert on the Aiscosity of whej^ will 

 not therefore be apparent from the results obtained by Ibllowing the jiresent method." 



The author concludes that the investigation does not show the cause 

 of the characteristic influence of heat on the physical condition of 

 milk and cream, but since it is also apparent in milk nearly free from 

 fat (centrifugal skim milk) as well as in full milk and cream, and 

 since the changes occur even below the melting point of milk fat, he 

 believes that this change from pasteurizing can not be attributed to 

 the fat globules. He suggests that these changes may be due ''to the 

 unstable character of the nitrogenous or the mineral constituents." 

 The subject is to be further studied, 



A new process for separating butter from cream, B. Grosch 

 {French Patent ^o. 35823d; abs. hi IikJ. Ayr. Prof/., 5 {1S97), Xo. 112, 

 i). 555).— Fresh cream is submitted to a natural lactic fermentation 



