INFLXTENCE OF TEMPERATURE 21 7 



This indicates the importance of temperature regulation in the fer- 

 mentation industries. Even pure cultures may give different products 

 if working at different temperatures. Cream ripened with a pure 

 culture starter at too high a temperature will have a sharp acid flavor. 

 The cold curing of cheese has become a very common practice because 

 of the much improved flavor. Bioletti claims that the value of the dry 

 California wines would be doubled if the fermentation were carried 

 on generally at a lower temperature. ^ 



End-point of Fermentation. — ^Another question is the relation 

 between the end-point of fermentation and the temperature. Of the 

 few data existing, many indicate that at a lower temperature the final 

 fermentation goes farther than at a higher temperature. Miiller- 

 Thurgau found that under exactly the same conditions with the tem- 

 perature as the only varying factor the following final amounts of 

 alcohol were produced by a pure culture of yeast: 



At 36° 3.8 per cent alcohol. 



At 27° 7.5 per cent alcohol. 



At 18° 8.8 per cent alcohol. 



At 9° 9.5 per cent alcohol. 



Concerning the lactic fermentation some investigators find no differ- 

 ence in the end-point, while others obtained results similar to the re- 

 sults with alcohol. With three strains of Bad. lactis acidi were ob- 

 tained after thirty-four days, by C. W. Brown: 



A B C 



At 37° 0.89 per cent 0.87 per cent 0.60 per cent of lactic acid. 



At 30° 1 .00 per cent 0.96 per cent 0.81 per cent of lactic acid. 



At 18° 1.08 per cent 1.06 per cent 0.88 per cent of lactic acid. 



At 6° 0.70 per cent 0.73 per cent 0.62 per cent of lactic acid. 



These results are quite logical and perhaps can be explained by 

 the recognized experience that all products of fermentation tend to 

 check the process of fermentation, and that any chemical product 

 or substance acts the more vigorously upon any life process the higher 

 the temperature. The same amount of alcohol that will still allow a 

 slow fermentation at 10° may check the fermentation entirely at 20°. 

 Naturally the rate of fermentation in the beginning will be higher at 

 the higher temperature but the end-point is lower. The end-point of 

 the lactic cultures A, B, and C at 6° is probably not final, because 



