508 EXPEEIMENT STATION KK(M)RD. 



milk was heak'd nii)i(lly l)y being in a thin layer, a tenn)erature of S0° C. for 2 min- 

 utes was snllicient to destroy the tul)ercle bacilH. This was not true in experiments 

 in which the temperature was 75° C. — f. w. woll. 



On the water content of butter, L. F. Rosengken {Landtmannen, 14 (1903), 

 No. 33, pp. 520-527). — A discussion of the various factors influencing the water con- 

 tent of butter, with the results of a number of experiments bearing upon this point. — 



F. W. WOLL. 



Report of Swedish butter exhibits, 1902, N. Engstrom [Meddd. K. Landtbr. 

 Styr. [Stveden'], 1903, No. S4, ]>p. 53). — The report presents the usual annual sum- 

 mary of the butter exhibits in Sweden. The number of creameries which took jjart 

 in the exhibits was 346. The total number of tubs of butter exhiliited and scored 

 was 1,491. The main results of the examination of the butter as to scores, water 

 content, loss of brine on storage, etc., are given in the report; as well as the average 

 results of examinations of skim milk, buttermilk, and butter made during the year. — 



F. W. WOLL. 



The role of the lactic-acid bacteria in the manufacture and in the early 

 stages of ripening of Cheddar cheese, H. A. Harding [Neiv York State Sta. Bid. 

 237, pp. 165-lSO). — In the introduction to this bulletin brief explanations are given 

 concerning 3 theories of cheese ripening namely, (1) that ripening is due mainly, 

 if not entirely, to lactic-acid ]>acteria, (2) that ripening is brought about by liquefy- 

 ing bacteria, and (3) that the breaking down of the casein is largely due to the 

 enzyms naturally present in milk. The results of some experimental work are 

 included, and other investigations at the New York State Station are referred to in 

 supijort of the views which are expressed concerning the role of lactic-acid bacteria 

 in the ripening of cheese. 



In factory milk lactic-acid bacteria are always present, and at the time of souring 

 commonly make up more than 95 per cent of the total number. The rapid develop- 

 ment of the lactic-acid bacteria checks the growth of other species, due to the 

 conversion of milk sugar into lactic acid. The action of this acid has been found in 

 practice and shown experimentally to hasten the curdling action of rennet. Inves- 

 tigations have shown that the lactic acid combines with paracasein to form 2 salts, 

 one the unsaturated j^aracasein monolactate, insoluble in water but soluble in dilute 

 salt solutions, and the other the saturated paracasein dilactate, insolpble in both 

 water and dilute salt solutions. 



That paracasein monolactate is formed in cheese curd l^y lactic-acid bacteria was 

 shown experimentally as follows: Fresh milk was curdled by rennet in the presence 

 of ether to prevent bacterial growth, and the curd was washed with water to remove 

 the greater part of the sugar. After sterilization portions of the curd were inoculated 

 with lactic-acid bacteria, with and without the addition of sugar. Without the 

 addition of sugar only very small quantities of paracasein monolactate were formed, 

 while with the addition of sugar considerable amounts were produced. 



In normal cheese during the first week after it is made it is stated that from one- 

 half to three-fourths of the nitrogen is found in the form of paracasein monolactate. 

 In forming the amount of monolactate ordinarily present the bacteria use up an 

 amount of sugar equal to from 2 to 4 per cent of the weight of the cheese. The 

 presence of the monolactate is considered essential to the digestive action of the 

 rennet enzym. As the part played by the enzyms of the milk itself is not confined 

 to the first stages of ripening, this sul)ject is to be treated in a separate bulletin. 

 The action of rennet enzym is not believed to extend much beyond the formation of 

 peptones, leaving the formation of the simpler nitrogenous compounds characteristic 

 of a rijaened cheese to be explained in some other manner. 



Some changes in a ripening cheese, F. II. Hall et al. {New York State Sta. 

 Buls. 214, 215, 219, 231, 233, 236, 237, popular ed., pp. 14)-— This bulletin summarizes 

 the more important points brought out in recent investigations at the station, and 



