482 EXPERIMENT STATION RECORD. 



of these were overcome to considerable extent by allowing two curd to 

 become unusually sour before grinding-. 



The cause of blue spots in cheese, T. J. Klaverweiden {Milch 

 Zt(j., ;Jo (^<S'^i), ^'^o. -114, iW- -'^^O-'ilL^; Xo.35,p2h 558-5H0). — Considerable 

 trouble was experienced in Holland with cheese becoming streaked or 

 spotted with blue, aud the author made an investigation of the matter 

 which soon showed that the trouble was not due to bacteria primarily. 

 Qualitative analysis of the spotted cheese showed the presence of iron, 

 but no copi)er was found. Normal cheese gave a slight reaction which 

 was at first misleading, but afterwards proved to be due to phosphates. 



(.Quantitative determinations were then made by Oudeman's method, 

 which showed the following percentages of iron in different cheese: 



Per ceut 



Cheddar cheese 0. 0092 



Clear Gonda cheese 0. 0112 



Blued Gouda cheese No. 1 0. 0400 



Blue specks from the latter 0. 6809 



This method is said to sometimes give too high results. Another 

 method (formation of iron ahim and titration with hyposulphite in 

 in^esence of x^otassium iodid) gave the following amounts of iron: 



Per cent. 



Blued cheese No. 2 0. 0094 



Blued cheese No. 3 0. 0080 



Clear cheese : 0. 004G 



By this method the blued Gouda cheese contained 0.0083 i)er cent of 

 iron, and the blue specks from the same 0.14 per cent. 



The pre^:euce of iron was also clearly demonstrated under the micro- 

 scope, and the author concludes the blue coloration is due to particles 

 containing iron, which, however, appear often to be accompanied by 

 some other foreign substance. Lengthy studies were made to find how 

 these materials got into the milk or cheese. These led to no definite 

 conclusions, but the author suggests that the iron may come from using 

 ferruginous water, or rusty utensils, or may be due to bacteria, Creno- 

 thrixkiihnicma, which takes iron up from water and afterwards deposits 

 it as spots of iron oxid. The time of greatest prevalence of this micro- 

 organism, August and September, agreed in general with the occur- 

 rence of this cheese faul t. Not a single Cheddar cheese was found 

 which turned blue, and as the iron content of Cheddar cheese was low 

 the author regards this as supi^ortiug his conclusiou that iron is the 

 cause of the fault. 



Outlines of dairy bacteriology, H. L. Kcssell (Madison, Wis.: Published hij the 

 author, 1S94 ; pp. riII-\-lSG). — This is a short handbook intended primarily for 

 students in dairy schools. It attempts to present the principles of the science of 

 bacteriology in their relations to dairy problems, and to explain in a practical way 

 the methods of controlling the activity of bacteria so as to utilize them to advan- 

 tage to the dairy, aud to avoid the evil results which their unchecked growth may 

 cause. Of the three parts of the book the first treats of bacteria in general, their 

 structure and form, function aud distribution; the second of the relation of bacteria 



