EXERCISE 42 

 WHAT EFFECT HAS HEAT UPON THE YEAST PLANT AND FEKMENTATION ? 



Materials. Test tube or flask ; cotton batting ; the sugar solution used in the preceding exercise. 



Directions. Stir very thoroughly the fermenting sugar solution in the generator used in the 

 preceding experiment, and pour some of it into a flask or a test tube. Heat it to boiling temperature 

 for a few minutes, and then plug the flask or tube with a cotton stopper. Allow the tube to stand 

 for a day, and observe if fermentation continues. What is the effect of heat upon yeast plants ? To 

 what practical use could you put the information gained in this exercise ? 



Additional problems. How is it that cider or sugar solutions ferment even when no yeasts have been 

 purposely placed in them ? 



Why was a cotton stopper used in the above experiment instead of a cork or rubber stopper ? Why 

 use any stopper ? 



Does fermentation continue in bread after the bread is baked ? 



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