INFLUENCE OF TEMPERATURE. 157 



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. 



In the chapter on enzymes it was stated that the fermentations were 

 due to enzymes which are independent of the cell after they are once 

 produced. The question arises whether the optimum temperature of 

 growth coincides with the optimum temperature of fermentation. Too 

 little is known as yet about the nature of enzymes to make definite 

 statements. 



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 tempera- 

 ture 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 difference 

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

 alcohol. With three strains of Bad. lactis acidi were obtained after thirty- 

 four days, 



A. B. C. 



at 37 0.89 per cent 0.87 per cent 0.60 per cent of lactic acid, 



at 30 i. oo per cent 0.96 per cent o. 8 1 per cent of lactic acid, 



at 18 i. 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 



