Why ethanol vapor doesn't get trapped in bread dough, while CO2 does?

[lost captain]

TL;DR Summary

Why ethanol vapor doesn't get trapped in bread dough, like CO2 ? They are both gases in the oven but one escapes the complex gluten structure while the other get traped inside

In ethanol fermetation and especially when baking a bread: "Yeast organisms consume sugars in the dough and produce ethanol and carbon dioxide as waste products. The carbon dioxide forms bubbles in the dough, expanding it to a foam."
We learn that ethanol leaves the bread, it escapes the gluten structure, it vaporizes but CO2 gets trapped inside. Why is that?
They are both in gas form(inside the oven), they are both small molecules, they are both in the same oven temperature hence their kinetic energy will be the same.

 

[256bits]

TL;DR Summary: Why ethanol vapor doesn't get trapped in bread dough, like CO2 ? They are both gases in the oven but one escapes the complex gluten structure while the other get traped inside

In ethanol fermetation and especially when baking a bread: "Yeast organisms consume sugars in the dough and produce ethanol and carbon dioxide as waste products. The carbon dioxide forms bubbles in the dough, expanding it to a foam."
We learn that ethanol leaves the bread, it escapes the gluten structure, it vaporizes but CO2 gets trapped inside. Why is that?
They are both in gas form(inside the oven), they are both small molecules, they are both in the same oven temperature hence their kinetic energy will be the same.

Hi Lost Captain
The full quote from Wiki includes an alcoholic content of bread. ( the high value from the reference, rather than a range )
" Ethanol fermentation causes bread dough to rise. Yeast organisms consume sugars in the dough and produce ethanol and carbon dioxide as waste products. The carbon dioxide forms bubbles in the dough, expanding it to a foam. Less than 2% ethanol remains after baking"

I see nothing of

We learn that ethanol leaves the bread,

so it might be worthwhile to explain where you got that idea from.

Hint:
At room temperature, is CO2 a gas or a liquid?
At room temperature, is ethanol a gas or a liquid?
Is there any water in the bread, and if so, how might that effect the formation of the bubbles, be it either from CO2 or ethanol being the main culprit responsible for the leavening?

 

[lost captain]

so it might be worthwhile to explain where you got that idea from.

Most of the ethanol vaporizes, since the amount left on the bread is pretty less than the ethanol that was produced.
That's why i said ethanol leaves the bread.
(Of course i searched that online before making that statement, my source wasn't any scientific paper, just a typical google search)
So compared to the CO2 that is being traped inside the gluten structure, why the same doesn't happen to the ethanol vapor?

At room temperature, is CO2 a gas or a liquid?
At room temperature, is ethanol a gas or a liquid?

At room temperature CO2 is gas and ethanol is a liquid. But still even before puting the bread in the oven as long as the ethanol fermentation has started, CO2 gas gets trapped inside while ethanol vaporizes
In the oven they are both gases, shouldn't ethanol also be responsible for the creation of bubbles inside the dough, bubbles because of ethanol vapor.

Is there any water in the bread, and if so, how might that effect the formation of the bubbles,

Sure there is water, but i cant make the connection...maybe ethanol is diluted in water while CO2 isn't?


Also thank you very much for taking the time to reply.

 

[Mayhem]

Speculation:
At r.t, ethanol is a liquid and CO2 is a gas. Ethanol as it is formed is chemically mixed with water in the dough, whereas CO2 is physically trapped in the dough. Upon baking, the ethanol is therefore free to evaporate along with the water, whereas trapped pockets of CO2 will increase in size and set as the bread bakes. You'll also notice that when you bake bread, there is some bubbling in the dough, so not all CO2 is trapped.

Just a guess.

 

[256bits]

Sure there is water, but i cant make the connection...maybe ethanol is diluted in water while CO2 isn't?

Ethanol is fully soluble in water, wheras CO2 has a solubility very low.
Most of the bubbles produced at room temperature would be comprised of mainly CO2, and some ethanol due to its vapourization pressure at that temp, as well as some water vapour.
Note that the yeast at the beginning will convert the sugars by both processes of aerobic respiration, with production of water and CO2, as well as anaerobic fermentation, with production of ethanol and CO2. The ratio of these chemical procedures progresses from aerobic to anaerobic as the oxygen supply within the bread diminishes.
https://www.engineeringtoolbox.com/gases-solubility-water-d_1148.html

The bubbles formed at room temperature are mainly of CO2 composition.
In the oven as the temperature rises, the bubbles increase in size. A bit more ethanol vapourises contributing to some increase in size. Until the yeast is completely dead due to the heat, more CO2 is being produced. Most of ethanol is still being absorbed by the water in the bread.

The final result is that the bubbles form from CO2 gas being given off from the yeast, the ethanol remains as a soluable mixture with the water in the bread.

Some evaporation of water and alcohol does occur during baking, but to what extent I would have to investigate, but just enough to give the bread its body.
A bread without enough water content is labelled as being dry.

 

[256bits]

the ethanol is therefore free to evaporate along with the water

Not all the water nor ethanol is removed from the bread during baking.
A fairly good percentage remains.
Nothing like the smell of freshly baked bread from what does escape.

 

[256bits]

There is this
https://dietandfitnesstoday.com/water-in-bread.php
of which some percentage, or grams, is alcohol in 100g.

Below is a summary list for the top twenty bread items ranked by the amount or level of water in 100g.

1. Breadfruit, raw : 70.65g
2. Bread stuffing, cornbread, dry mix, prepared : 64.90g
3. Bread stuffing, bread, dry mix, prepared : 64.77g
4. Bread, kneel down (Navajo) : 52.96g
5. Bread, wheat, sprouted : 50.88g
6. Bread, boston brown, canned : 47.20g
7. Bread, wheat, sprouted, toasted : 46.61g
8. Bread, reduced-calorie, oat bran : 46.00g
9. Bread, reduced-calorie, rye : 46.00g
10. Bread, reduced-calorie, oatmeal : 44.00g
11. Bread, oat bran : 44.00g
12. Bread, gluten-free, white, made with rice flour, corn starch, and/or tapioca : 42.99g
13. Bread, reduced-calorie, white : 42.90g
14. Bread, cinnamon : 41.93g
15. Bread, rice bran : 41.00g
16. Bread, protein (includes gluten) : 40.00g
17. Bread, french or vienna, whole wheat : 39.81g
18. Bread, reduced-calorie, wheat : 39.60g
19. Bread, white wheat : 39.60g
20. Bread, cornbread, prepared from recipe, made with low fat (2%) milk : 39.10g

 

[Mayhem]

Not all the water nor ethanol is removed from the bread during baking.
A fairly good percentage remains.
Nothing like the smell of freshly baked bread from what does escape.

Of course not, but a significant amount must.

 

[DrJohn]

As water is also formed during the fermentation in bread, and has the highest boiling point of the three - water, ethanol, and carbon dioxide - as a guess, perhaps it too is contributing to the bubble size inside the bread, with more of the carbon dioxide and ethanol escaping than the water?

This is just a suggestion, something that might be happening, perhaps.

 

[256bits]

Of course not, but a significant amount must.

each reader will have their own meaning of 'significant' and may not be in sync with what the writer thinks he has implied.

A quick and easy perusal on the web led to this bakery discussion,
Bread loses 10-25% of its original dough weight through the production process. The majority of the weight is lost through moisture loss during proofing, baking and as the bread cools. Home bakers and small bread producers should expect a weight loss of about 15-20%. While large-scale baking plants can use special cooling units to reduce weight loss to around 12-13%.

https://www.busbysbakery.com/bread-weight-lost-when-baked/

Did you even look at the above table
16. Bread, protein (includes gluten) : 40.00g per 100g

A typical recipee
Ingredients

• 2 ¼ teaspoons yeast
• 1 teaspoon Granulated Sugar
• 1 cup water - 240 g
• 2 ½ cups All-Purpose Flour (or bread flour) - 325 g
• 2 tablespoons Olive Oil
• 1 teaspoon salt

dough - 43 % water
bread - 40 % water

 

[256bits]

As water is also formed during the fermentation in bread, and has the highest boiling point of the three - water, ethanol, and carbon dioxide - as a guess, perhaps it too is contributing to the bubble size inside the bread, with more of the carbon dioxide and ethanol escaping than the water?

This is just a suggestion, something that might be happening, perhaps.

Even if a suggestion, it should be backed up by science to confirm or deny.
https://www.chemguide.co.uk/physical/phaseeqia/nonideal.html

 

[JT Smith]

We learn that ethanol leaves the bread, it escapes the gluten structure, it vaporizes but CO2 gets trapped inside.

We certainly did not learn that from the entry in the Wikipedia page. It only states that CO2 is responsible for some part of the formation of the dough foam. It says nothing of the fate of the ethanol vapor.

Certainly some ethanol remains in bread. It's a moist product so it's an example of distillation: some of the ethanol will remain. You can smell it. It's likely the case that some of the ethanol vapor contributes in a small way to the formation of the dough foam. Another contributor is water vapor during the early stages of baking. That's called "oven spring" and if you bake bread (and watch it) it makes you smile.

 

[lost captain]

Maybe i shouldn't have emphasized on the amount of ethanol that evaporates rather why it evaporates more than CO2? But am i even right on this one? Does ethanol evaporate more from the dough than CO2 that is being traped inside the gluted structure? If so why?

 

[lost captain]

The final result is that the bubbles form from CO2 gas being given off from the yeast, the ethanol remains as a soluable mixture with the water in the bread

But ethanol becomes vapour in the oven, how does it stay as soluble mixture with water?

 

[lost captain]

We certainly did not learn that from the entry in the Wikipedia page.

Yeah i shouldn't have written it like that.
What i wanted to say is that when i searched about ethanol online and where does it go while baking the bread (because certainly most of it doesn't stay in the bread, cause bread doesn't taste like alcohol)
I've found that most of it vaporizes in the oven.

 

[Fra]

Also not that only a tiny amount of ethanol is produced in a dough fermentation in the first place as compared to the volume co2, because there are no massive amounts of sugar in dough to make bread. So the small amount of CO2 from fermentation required to raise a dough enough, will yield very small amount of ethanol and would be unlikely be enough to make the bread taste like alcohol even IF it was left, neither would it make you drunk.

/Fredrik

 

[DrJohn]

Even if a suggestion, it should be backed up by science to confirm or deny.
https://www.chemguide.co.uk/physical/phaseeqia/nonideal.html

Totally agree, but it was almost midnight uk time, I had had some wine, which clearly contained alcohol , and my lady was urging me to come to bed . And I thought "spell azeotropic mixture to find graphs for extra info? - nah go to bed".
I'd already found articles about ethanol in bread formation, almost certainly one that has been quoted above.
Luckily you did the extra work.
I added "just a suggestion" as a get out of jail excuse for not adding more scientific evidence....

 

[JT Smith]

Does ethanol evaporate more from the dough than CO2 that is being traped inside the gluted structure? If so why?

I don't see why ethanol would be more likely to escape the foam cells than CO2. Ethanol is a larger molecule so if there is a difference I would imagine it less likely to escape. But a lot of CO2 and ethanol that is produced during bread baking is purged when the bread is punched down after each rising. It's only in the final proof stage that the gas is allowed to remain.

As far as how much of each remains in solution I'm not sure. The solubility of CO2 decreases with temperature and 100°C it's pretty small. The ethanol fraction that remains is more a function of how much of the solution vaporizes. The temperature is of lesser importance. That is to say, if you evaporate some fraction of a water/ethanol solution at room temperature you'll end up with a similar amount of ethanol remaining as you would if you boiled it.

 

[JT Smith]

But ethanol becomes vapour in the oven, how does it stay as soluble mixture with water?

Because that's how it works. Ethanol and water are fully miscible. When some of the solution is vaporized the ethanol, being more volatile, vaporizes at a greater rate percentage-wise. But as the concentration of ethanol decreases the actual amount vaporizing in each gram of solution also decreases. So it's never zero. You can boil a bottle wine down to a milliliter and there will still be some ethanol in it.

 

[symbolipoint]

Why ethanol vapor doesn't get trapped in bread dough, like CO2 ? They are both gases in the oven but one escapes the complex gluten structure while the other get traped inside

There are plenty of response posts already, but NEITHER of those compounds remain trapped. Both volatile.

 

[JT Smith]

In the short term, while the dough is rising, their ability to escape is limited. That's what makes the bread rise. Longer term they will escape.