806 EXPERIMENT STATION EECOKD. 



to rennin may be produced by any proteolytic eizym. Work along this line is 

 being carried out by the author. 



" In the light of the results reported in this paper, togethCT witii those of 

 Van Slyke and Bosworth [see above], the retarding action of soluble salts of 

 ammonium, sodium, and potassium on the coa^lation of milk or casein solu- 

 tions by rennin may be explained as follows: The addition of salts of these 

 bases to mUk or casein solutions results in a double decomposition whereby the 

 calcium caseinate is changed to a caseinate of the base added. These are con- 

 verted to paracaseinates by rennin, but owing to the fact that all the paracase- 

 Inates of these bases are soluble, no coagulation results." 



The copper stdphate serum prepared with milk according to Lythgoe, 

 B. ACKEEMANN and C. Valencien (Ztschr. Untersiich. Nahr. u. Geniissmtl., 24 

 {1912), No. 10, pp. 612-614). — The authors conclude that the method recom- 

 mended by Lythgoe (E. S. R., 24, p. 514) for preparing milk serum for refracto- 

 metric purposes in the eiamination of milk for the purpose of detecting added 

 water has no advantages over the calcium chlorid method. It yields a very 

 clear serum in the cold, but about 20 per cent of its accuracy is lost by the 

 dilution of the milk serum. 



The casings of the milk fat globules, G. A. Bredenbeeg (Abhandl. Affr. 

 Wiss. Gesell. Finland, 1912, No. 4, pp. 62). — The results obtained with whole 

 milk, cream, butter, and olive oil show that at least 2 kinds of casings or mem- 

 branes can be prepared with fat droplets, and that these processes play a 

 greater part than has been previously supposed. A butter emulsion, for in- 

 stance, if free fatty acids are present, will form a casing with lime water. 

 This is due to the formation of a compound between the calcium and oleic acid, 

 butyric acid, etc. 



The protein content of the casing (9 to 13 per cent) is not a part of the 

 casing substance, but simply represents particles of casein which are distributed 

 throughout the butter. Samples of gravity fat obtained from skim milk were 

 found to be much lower in calcium and higher in protein than the casing sub- 

 stance from the globules of the butter. The traces of fatty acids which are 

 also present in fresh milk take part in the formation of the membranes. When 

 a large amount of calcium is present in the casings, the formation of insoluble 

 lime salts must also be considered. The high calorific value of the casing sab- 

 stance indicates a nitrogen-free organic material. 



The reaction of milk to certain reagents, Bordas (Orig. Comnvun. 8. Inter- 

 nat. Cong. Appl. Cliem. [Washington and New York], 18 {.1912), Sect. VIIIc, pp. 

 69-72; abs. in Ghent. Ztg., 36 (1912), No. 134, P- 1312).— The bine coloration 

 produced in mUlv with hydrogen i>eroxid and paraphenylendiamin is not dne to 

 a simple oxidation process, but to the action of a substance intermediate be- 

 tween paraphenylendiamin and quinone upon the calcium salts. The reaction 

 proceeds in 2 stages: (1) The paraphenylendiamin is oxidized by a catalytic 

 process; (2) the oxidation products bring about the blue coloration through the 

 agency of the calcium salts. 



According to present theories fresh milk contains ensgrms which are capable 

 of decomposing hydrogen peroxid, and the blue coloration is due to the resulting 

 liberation of oxygen. It is, however, a known fact that a milk heated to 80* C. 

 is not capable of liberating oxygen from hydrogen peroxid. According to the 

 author, if such a milk is centrifuged, the catalyzer can be isolated, and this 

 catalyzer, when added to homogenized milk which has been previously heated 

 to 80°, produces a reaction with paraphenylendiamin, altiiou^ it is much 

 weaker than the one given by fresh milk- 



