191S.] DAIRY FARMING DAIRYING. 881 



the case of the flash process, to 1.7 cts., in the case of the holding process, 

 higher In price tlian tiae butter made from raw cream. 



Tlie holding process of pasteurization at 145° was most efficient, averaging 

 over 99.9 per cent in its germ-killing effect on all types of microorganisms. 

 The flash process at 185° lacked uniformity, and at 165° was deficient in germ- 

 killing efficiency. The germ-killing efficiency of pasteurization in summer was 

 greater and the keeping quality of such butter was better than that of winter 

 cream and butter. However, pasteurization at 145° holding process destroyed 

 over 99 per cent of the germ content of cream, regardless of the season of the 

 year and variations in the resistance of different types of germs. 



In order to test the effect of time of holding cream at 145° on the germ-kill- 

 ing efficiency and on the keeping quality of butter, cream was held at this 

 temperature for 10, 15, 20, 30, and 40 minutes. From the standpoint of the keep- 

 ing quality of the butter 20 minutes' holding proved best. The greatest reduction 

 of microorganisms occurred when the cream was held at 145° for 40 minutes, 

 and tlie germ-killing efficiency was greatly diminished when the time of ex- 

 posure was shortened to 15 or 10 minutes. Butter from cream held at 145° 

 for more than 20 minutes, however, contained as large numbers of liquefiers, 

 yeasts, and molds as when held for 20 minutes only, and exposure at 145° for 

 longer than 20 minutes was found to produce a mealy body in the butter under 

 certain conditions. 



Anotlier experiment demonstrated the necessity of guarding against recon- 

 tamination after pasteurization. It has been found that an unclean vat may 

 reduce the efficiency of pasteurization 50 per cent. It was also shown that the 

 better the flavor and the lower the acidity of the cream at .the time of pasteuri- 

 zation, the better will be the flavor of the butter when fresh and when it comes 

 out of storage. 



In 104 churnings the average percentages of fat In the buttermilk were as 

 follows : From raw cream 0.101, and from pasteurized cream at 145° held 20 

 minutes 0.137, at 165° flash 0.12, and at 185° flash 0.12. In these churnings 

 there was a somewhat larger loss of fat from the high-acid cream than from the 

 low-acid cream. 



Pasteurization of cream had very little effect on the chemical composition 

 of the butter. The moisture, curd, and acid were somewhat lower in the 

 pasteurized cream butter than in the raw cream butter, and the highest tem- 

 perature used for pasteurizing showed the greatest difference. There was a 

 gradual decrease in lactose and increase in acidity of the raw and pasteurized 

 cream butter after three months' storage ; however, the raw cream butter in- 

 creased far more rapidly in acidity than the pasteurized cream butter. There 

 was also a decrease in the acidity of the fresh butter, due to pasteurization. 

 The fat constants in butter in storage were found to undergo but very slight 

 changes, and these changes averaged somewhat greater in raw cream butter 

 than in pasteurized cream butter. Results of monthly analyses of milk fat 

 held for one year at ordinary room temperature show that the fat constants 

 in the stored fat underwent very slight changes, not at all commensurate with 

 the degree of rancidity and tallowiness developed in the fat. 



The hydrolyzed or cleavage products of the proteins in butter were deter- 

 mined in 64 separate churnings of the butter from raw and pasteurized cream, 

 when the butter was fresh, and after storage at —6° for one, three, and five 

 months, respectively. The results indicate that some protein decomposition 

 takes place in all butter during storage even at a temperature below 0°, and 

 it is suggested that this protein hydrolysis may, in a large measure, be re- 

 sponsible for off flavors in storage butter. Butter that is intended for pro- 

 longed storage should, therefore, be as free as possible from curd. It is also 



