10201 DAIRY FARMING DAIRYING. 681 



Whon cultivated in rnill< many of the lactic acid bacteria were observed to 

 l)rodu(v sllnic. imrticularly at low temperatures, tbrouKl» the swelling up of 

 the more or less distinct capsules surrounding the colls at certain stages of the 

 culture. Streptococcus cremoris (new name), the distinctive organism in 

 starters Used in butter making, also produced ropy milk. The best strains of 

 8. cremoris for butter making seem to have the least power of fermenting sac- 

 charose, maltose, and dextrin. 



Some results with experimental cheeses made from practically germ-free 

 milk inoculated with pure cultures of lactic acid bacteria are briefly reported. 

 In all cases putrefactive fermentations were greatly reduced. Strcptohacterium 

 casci (=Bactcrium ca!<ci a) was the most satisfactory when high temperatures 

 are not used in the process of manufacture, with Streptococcus lactis (=/S. 

 tactions) and S. cremoris next in value. Tetracoccus liquefaciens {=]ilicro- 

 coccus casci liquefaciens) made the cheese rather soft and imparted a flavor 

 resembling " Danish Swiss " or " liussian Steppe " cheese. For cooked cheese, 

 previous results indicating the value of Thermohacterium helveticum {—Bac- 

 terium casei e) are confirmed. The thermobacteria are characterized by 

 ability to withstand heat. 



Rehition between lactic acid production and bacterial growth in the 

 souring of milk, J. C. Baker, J. D. Bkew, and H. J. Conn {New York State 

 Sta. Tech. Bui. 74 {1919), pp. 24, figs. 5). — Two samples from the same cow of 

 pasteurized skim milk low in bacteria were each inoculated with a different 

 culture of Streptococcus laciicus and incubated at 25° C. Determinations of 

 acidity and number of bacteria were made at hourly or half-hourly intervals 

 through 10 iiours, beginning 15 hours after inoculation. Loss systematic ob- 

 servations were made at later periods, and some supplementary data were 

 secured from other cultures. 



In one case the expected increase in number of bacteria (a doubling every 

 generation) was approximately realized, but in the other case the rate of mul- 

 tiplication was much slower and remained fairly constant throughout the period 

 of systematic observation. This behavior is attributed to the attenuated nature 

 of the original culture (an old butter starter) ; the milk was not curdled in 24 

 hours, and it is thought that many of the organisms had lost the power of 

 growth. 



In each case the amount of acid produced was approximately proportional to 

 the number of bacteria present. In a vigorous culture an individual cell pro- 

 duced between 5X10—" and 10X10—" mg. of lactic acid per hour. The much 

 higher average figure (18X10—") given by Rahn (E. S. R., 26, p. 70S) is deemed 

 subject to correction, since it is based on plate counts. The authors' deductions 

 are drawn entirely from direct microscope counts, although plate counts were 

 made for comparison. The former avert! ged 1.8 times the latter, and the latter 

 were approximately equal to the estimated number of isolated groups counted 

 by the microscope. 



At the time of curdling, the milks contained several billion bacteria per cubic 

 centimeter. The rate of nmltiplication became slower after coagulation and 

 acid formation declined. 



Determination of keeping quality of milk, L. H. Cooledge {Michigan Sta. 

 Quart. Bui., 2 {1920), No. 4, pp. 168, 169).— The author cites data illustrating 

 the value of the milk scoring method of Cooledge and Wyant (noted on p. 615) 

 in estimating the keeping quality of milk samples. 



The question of city milk distribution, F. L. Thomsen {Hoard's Dairi/- 

 man, 59 {1920), No. 8, pp. 453, 461-410, figs. 3).— Eleven plans for the distribu- 

 tion of milk in cities are outlined. 



