New YorK AGRICULTURAL EXPERIMENT STATION. 87 
to 75° F. (18° to 24° C.); in the second, from 70° to 80° F. 
(21° to 27° C.). In another ‘set of experiments, we used 3000 
cc. of pasteurized separator skim-milk, to which had been added 
50 ce. of a sour-milk starter. We placed in each of 14 cotton- 
stoppered flasks 100 cc. of this milk and allowed one lot (3) to 
stand at a temperature of 60° to 70° F. (15.5° to 21° C.) and 
another lot (4) at a temperature of 70° to 80° F. (21° to 27° C.). 
In this second set of experiments, we used the contents of one 
flask for making an analysis at each stated period of time, no 
flask being opened until its contents were used. The results of 
these experiments are given in the table below: 
TABLE I—SHOWING CHEMICAL CHANGES IN THE SOURING OF MILK. 
| Percent- | Percent- 
No. Age of |Amount) Amount | Amount} Propor- age of age of 
of milk of milk-| of milk- | of lactic} tion of nitrogen | caseinin | Coagu- 
ex- when sugar in sugar acid in | sugar in | in milk in form of | lated. 
peri- | analyzed. milk. changed. milk. milk soluble mono- 
ment | changed. form. lactate. | 
Hours. Per ct. Per ct. Per ct. Per ct. Per ct. Per ct. 
1 Fresh. SU) |) ————$_——= = | | 
2 Fresh. 5.58 | 
3 Fresh. 5.08 | 0.187 
4 Fresh. 5.08 0.187 
1 8 4.53 0.62 | 12.04 | 
2 8 5.25 0.33 5.91 
3 8 4.53 0.55 | 0.011* 10.83 
4 | 8 4.32 0.76 | 0.081 14.96 
| 24 4.25 0.90 ree oe ee ee Serie 
2 24 4,42 | 1.16 20.-.80 21.19 12.70 | ) lated. 
13 24 4.00 1.08 | 0.506* 21.26 | ———— | —— | { coagu- 
4 24 3.79 1.29 .776* 25.40 | ————— | ———— | ) lated. 
3 26 3.92 1.16 | 0.596* PAE 03) | | I iE 
1 294 3.88 1.27 24.66 17.44 14.43 | | lated. 
1 32 sega 1.44 | —— — 28.00 22.61 | 13.18 
2 32 4.20 1.38 24.73 22.68 | 11.50 
3 32 3.86 1.22 | 0.740* 24.00 
4 32 3.76 | 1.32 | 0.848* 26.00 | 
et 48 3.70 | 1.45 Wa Sta 22.80 10.20 
2 48 4.18 | 1.40 25.10 21.19 8.61 
3 48 3.79 |} 1.29 | 0.821* | 25.40 
4 48 3.76 | 1.32 | 0.848 | 26.00 
| | 
1 | 72 it 3166 1.50 29.13 24.14 | 8.00 
2 | 72 4.13 1.45 | 26.00 21.38 8.61 
3 | 72 SEG at 1.32 | 0.839% | 26.00 | 
4 72 3.02 | 1.36 | 0.857* 26.77 
1 96 3.66 1.49 | 28.93 23.95 | 6.70 
2 96 4.07 | 1 aii! | 27.06 22.87 | 6.00 
3 | 96 3.70 1.38 | 0.875* | 27.16 
4 96 3.69 1.39 | 0.884* | 27.36 
| 
2 120 4.07 oil | 27.06 22.68 5.74 | 
3 120 3.62 1.46 | 0.893* | 28.74 
4 120 3.64 | 1.44 | 0.884 * 28.35 
| | | 
*Amount of lactic acid less the amount of acid in the fresh milk. 
