This experiment as been done at various levels with different starch sources. In order to increase the skill level for this experiment, I introduced an analysis of glucose and/or reducting sugars this year.
Summary of procedure:
A suitable source of starch is boiled, cooled, and digested with amylase enzymes.
The starch source is fermented with yeast for a week.
The ethanol is distilled from the fermentation mixture and analyzed for ethanol content with refractive index.
Positive:
+It is a very accessible experiment that has some practical value.
+Measuring the alcohol content by carbon dioxide loss and direct distillation of ethanol gives an interesting comparison.
+The analytical value of the experiment can be increased by measuring the glucose and/or reducing sugar content before the starch source is fermented and by measuring the ethanol content of the fermented mixture by various methods.
Neutral:
±It has to take two weeks.
Negative:
- It is not a very advanced experiment.
Inquiry & Extension Ideas:
●Various starch sources can be investigated. I was suprised to discover that pre-soaked minute rice yields much more alcohol than the "traditional" frozen sweet corn.
●Different modes of preparation could be compared. What is the contribution of boiling, adding buffer, amylase, and amyloglucosidase to the process?
Student Comments 2009
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