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Biology/Yeast Turning Dough into an Intoxicant


QUESTION: Dear Mr. Walter Hintz,

I thought about whether or not putting yeast in the dough would turn the dough into an intoxicant, meaning something that can cause drunkenness in humans. We know that yeast turns sugars into ethyl alcohol and carbon dioxide: One molecule of glucose turns into two molecules of ethyl alcohol and two molecules of carbon dioxide.

What I did was compare the amount of sugar in grape juice to the amount of sugar in dough made with white flour. Before mentioning the numbers, I want to say that to make one cup of dough, you need one cup of flour. Contrary to what some people might think, adding water does not increase the quantity. If you have half a cup of flour, and then you add water to turn it to dough, you would still get about half a cup of dough.

Everyone would agree that if the sugar in grape juice ferments, the juice will turn into an intoxicating drink. Putting yeast in the juice would do this. One cup of grape juice happens to have about 36 grams of sugar, and one cup of dough made with white flour happens to have about 95 grams of sugar.

Therefore, my conclusion was that when yeast is put in the dough, it becomes more than twice as intoxicating as fermented grape juice, as the alcohol in it is such. Disagreeing with that would be contradicting simple mathematics. Yes, most or all of the alcohol evaporates during baking, and the bread itself cannot cause drunkenness. But I am not concerned with the bread.

So at the end, I ask you if you agree that putting yeast in the dough turns it into an intoxicant.

ANSWER: Hi Abdullah
I agree that yeast causes fermentation in bread dough. It all depends upon temperature. Yeast reproduces at about 85 % F causing the formation of CO2. During baking the higher temperatures kills the yeast cells before alcoholic fermentation takes place

---------- FOLLOW-UP ----------

QUESTION: Thanks for your answer, Mr. Hintz. We know that carbon dioxide makes the dough rise. Different sources say that the yeast in the dough breaks sugars into ethyl alcohol and carbon dioxide. So if the dough rose, then alcohol fermentation has already taken place, because yeast produces both. Different sources also mention that the alcohol produced by yeast fermentation evaporates during baking. This means alcoholic fermentation happens during the rising process before the dough even goes in the oven.

If all the sugar in the dough is turned into ethyl alcohol and carbon dioxide, the amount of alcohol in it would be more than the amount of alcohol in fermented grape juice which definitely intoxicates. So there is no way to say the dough does not turn into an intoxicant if all the sugar ferments, right?

Fermentation of sugar in bread is a secondary reaction. Yeast enzymes first catalyze glycolosis and the sugar is converted to Pyruvate. Under fermentation pyruvate is degraded to ethanol and CO2. The sugar does not ferment,the pyruvate ferments and in the process CO2 bubbles form as does ethanol nut just about all of the alcohol does not accumalate but is lost in the process. The bread contains less then 1% ethanol


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Walter Hintz


Science teacher for over 50 years. MSc. in biology. I can answer questions in general biology, zoology, botany, anatomy and physiology and biochemistry.


I have a MSc in biology and have been a science teacher for over 50 years. At present I am a faculty member at a college and a science consultant at seven catholic schools.

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