936 



Journal of Agricultural Research vol. vi, No. 24 



Table II. — Analysis of air extracted from butter made from sweet cream churned imme- 

 diately after the addition of 15 per cent of a commercial starter 



[Calculated to c o C. and 760 mm. Acidity of cream as lactic acid, 0.25 per cent; salt, 1.19 per cent; 



curd, 0.59 per cent] 



Number of bacteria per gram. 



680, OOO . 

 160, OOO . 



Oxygen. 



Per cent. 



10. So 



11. 64 

 10. 84 

 10. 70 

 10.95 



8.78 

 9. 00 



Carbon 

 dioxid. 



Per cent. 



26.44 



25-35 

 22.34 

 21.87 

 20. 92 

 19.27 

 19.50 



After the addition of a starter the acidity of the cream from which 

 the butter of sample 2 was made was a little more than twice that of 

 the cream used in the preparation of the sample of sweet-cream butter. 

 A slight but appreciable decrease in the oxygen content of the sample 

 during storage at a temperature of o° F. was observed, while a percep- 

 tible decrease in the carbon dioxid was also manifested. After the 

 sample had been kept for a period at a temperature of o° F., the effect 

 upon the composition of the air in the butter after standing for several 

 days at a temperature of 32 F. was tabulated, as shown in Table II. 

 This table also shows that a sample of butter made in this manner dis- 

 plays, so far as the composition of the air inclosed in it is concerned, a 

 comparatively slight variation from that observed in the previous case 

 of sweet-cream butter, when both samples are stored at a temperature 

 of o° F. This sample of butter scored 92 when made, 90 after three 

 months' storage at a temperature of o° F., and 89 after six and one- 

 half months' storage at the same temperature, there being practically 

 no variation in the flavor during the interval. 



The addition of lactic acid to the cream of butter sample 3 before churn- 

 ing brought the total acidity to nearly three times that of the cream 

 used to prepare the foregoing butter of sample 2, and about six and one- 

 half times that of the cream used in making the sweet-cream butter. A 

 pronounced decrease, greater than that observed in either of the two 

 previously given samples of butter, occurred in the oxygen and carbon- 

 dioxid content, even when the butter was stored at a temperature of 

 o° F., and this decrease was still more marked when it was allowed to 

 remain at a temperature of 32 F. The score of this butter, originally 93, 

 fell to 88 after three months in storage at a temperature of o° F., and at 

 the end of this interval it had an unclean flavor which was still more 

 pronounced after a period of six months' storage at the same tempera- 

 ture, when the score was 84. 



