274 



The Philippine Journal of Science 



of alcohol, so that the fermentation period is prolonged. Ex- 

 tremely prolonged periods of fermentation are to be avoided, 

 since solutions are liable to bacterial infection and consequent 

 loss of alcohol. On the other hand, dilute solutions cost more for 

 distillation and require more space for handling; consequently 

 yeasts that will quickly ferment concentrated solutions are to be 

 preferred. 



The temperature for fermentation is dependent to some extent 

 on the yeast used. Investigation has proved that temperatures 

 below 30° C. are usually best. High temperatures are favor- 

 able for bacterial growth, especially acid-forming bacteria, and 

 the loss of alcohol resulting from evaporation is greater. When 

 the yeast causes fermentation, considerable heat is liberated, 

 and unless cooling coils are used, the temperature of the fer- 

 menting vat rises. In the Philippine Islands, where the usual 

 atmospheric temperature is 30° C, the temperature during fer- 

 mentation rises as high as 45° C. in some cases. 



EXPERIMENTAL PART 

 The solutions of, molasses used were in every case sterilized 

 after the sulphuric acid was added. Tests were made on the 

 yeast to determine what temperature it is capable of enduring 

 without having its powers of reproduction destroyed. Ten per 

 cent molasses solutions were sterilized and then inoculated from 

 the stock culture of the yeast, with the results recorded in 

 Table V. 



Table V. — Effects of heating at various temperatures for ten minutes on 

 the yeast found in the fermenting nipa juice. 



Initial treatment. 



Control; sterilized wort; no 



inoculation. 

 Control; inoculated; not 



heated. 

 Inoculated; heated to40°C. 



Inoculated; heated to 46° C. 



5 (in duplicate) ... Inoculated; heated to 50° C. 



6 (in duplicate) ' Inoculated; heated to55°C. 



7 (in duplicate) .. Inoculated; heated to 60°C. 



8 (in duplicate) _J Inoculated; heated to 65 C C. 



9(in duplicate) .. Inoculated;heatedto70°C. 



Condition at end i 



Sterile Sterile. 



Solid mass of cells. 



Not so numerous as in 2 



Fewer than in 3. Healthy 



condition. 



.—do 



Scattering clusters of 



cells. 



do 



Scattering cells -- 



Condition poor | Good condition 



No cells discernible. Sterile. 



Same as at end of 28 



hours. 

 Well developed; 



good condition. 

 Do. 



Do. 

 Yeast very plentiful. 



Heating for ten minutes has a slight effect at 40° C, hut the 

 shock from heating for this length of time is not severe until 



