Cooking food...

[rivan]

I'd imagine there's no single answer; it would likely depend on the specific compounds being cooked, but:

Does cooking food end in a higher net energy in the finished product? What about foods that are twice-cooked? Is there a threshold (burned?)

Dough->bread->toast?

 

[Gibsons]

Cooking will break a lot of bonds so in theory there's a lot energy that's removed. But digestion does similar things anyway. On the other hand, some things are maybe not digestable or at least very hard to digest, until cooked.

Bread should have less total caloric content than dough, the yeast will metabolize carbohydrates to ethanol and CO2.

 

[BrownTown]

I would expect that cooking would lower the total energy of foods by breaking many of the bonds. Burt foods definitely have considerably less caloric usage. However, as mentioned before, what really matters is bioavailability of the calories, so its entirely possible for some foods that you are breaking up bonds that your body could not break and therefore increasing the caloires available to your body. Certainly by no whatsoever are you adding energy even remotely resembling the amount of energy used in the cooking process.

 

[rivan]

Originally posted by: Gibsons
Cooking will break a lot of bonds so in theory there's a lot energy that's removed.

Is this universally true, or does it depend on what's being cooked? Is the energy released eventually radiated as additional heat, limited by the heat retention properties of the mass?

Bread should have less total caloric content than dough, the yeast will metabolize carbohydrates to ethanol and CO2.

Yet that ethanol has energetic potential of it's own, does it not? And some would certainly be retained as added yeast mass.

And what about the bread->toast step? What's the difference in stored energy before and after a slice is toasted? Is there a net change? I'd think so, since the bread browns.

Pick another example, if that one's a poor choice for some reason - say an uncooked->cooked egg.

 

[rivan]

Originally posted by: BrownTown
Burt foods definitely have considerably less caloric usage.

That's somewhat intuitive - but before reaching the "burnt" stage is less so. Actually, that's what prompted me to consider 'threshold' portion of my questions.

However, as mentioned before, what really matters is bioavailability of the calories, so its entirely possible for some foods that you are breaking up bonds that your body could not break and therefore increasing the caloires available to your body. Certainly by no whatsoever are you adding energy even remotely resembling the amount of energy used in the cooking process.

I'm considering this on an academic level - I'm less concerned with the idea that I could make food more nourishing than I am with thinking about where the energy ends up.

It all started with the most excellent meatloaf last night...

 

[Gibsons]

Originally posted by: rivan

Originally posted by: Gibsons
Cooking will break a lot of bonds so in theory there's a lot energy that's removed.

Is this universally true, or does it depend on what's being cooked? Is the energy released eventually radiated as additional heat, limited by the heat retention properties of the mass?

Bread should have less total caloric content than dough, the yeast will metabolize carbohydrates to ethanol and CO2.

Yet that ethanol has energetic potential of it's own, does it not? And some would certainly be retained as added yeast mass.

And what about the bread->toast step? What's the difference in stored energy before and after a slice is toasted? Is there a net change? I'd think so, since the bread browns.

Pick another example, if that one's a poor choice for some reason - say an uncooked->cooked egg.

I'm not sure if it's universally true, there might be some foods that are an exception. Generally speaking though, the heat from cooking (and maybe the acid or even some proteases) causes breaking of bonds that contain energy. They'll release the energy as a small amount of heat.

As for the ethanol, yes, the ethanol has energy, but not nearly as much as the carbohydrates used to make it.

Just an educated guess, but I think a fried egg and a raw egg would have nearly identical calories. The main change is just denaturing the proteins, which really doesn't change the caloric content.

 

[PlasmaBomb]

They'll release the energy as a small amount of heat.

Breaking bonds is an endothermic process.

I think a fried egg and a raw egg would have nearly identical calories.

In the fried egg example it would probably end up with a higher calorific content as it absorbs oil while cooking. So the answer depends on your choice of cooking

 

[silverpig]

Originally posted by: PlasmaBomb

They'll release the energy as a small amount of heat.

Breaking bonds is an endothermic process.

I think a fried egg and a raw egg would have nearly identical calories.

In the fried egg example it would probably end up with a higher calorific content as it absorbs oil while cooking. So the answer depends on your choice of cooking

I was about to say that as well.


Breaking bonds TAKES energy. Creating bonds releases energy. This is in most cases of course.

 

[Gibsons]

Depends on what bonds are breaking and forming doesn't it?

Put ATP in water and heat it up and ATP--> ADP + Pi +energy/heat.

 

[rivan]

Originally posted by: PlasmaBomb

They'll release the energy as a small amount of heat.

Breaking bonds is an endothermic process.

I think a fried egg and a raw egg would have nearly identical calories.

In the fried egg example it would probably end up with a higher calorific content as it absorbs oil while cooking. So the answer depends on your choice of cooking

For the purposes of my question, you'd be including the oil in both the 'before' and 'after' calorie counts.

 

[silverpig]

Originally posted by: Gibsons
Depends on what bonds are breaking and forming doesn't it?

Put ATP in water and heat it up and ATP--> ADP + Pi +energy/heat.

The large majority of cases work the other way. So large in fact that the ATP reaction can be one of few examples to the rule.

 

[CycloWizard]

Cooking involves a few different thermodynamic "steps":
1. Sensible heat change (change in temperature),
2. Reaction (could be exothermic, those most are probably endothermic),
3. Phase change (always endothermic during heating), and/or
4. Other (such as pasta, which I believe is not a truly reactive system but involves water infiltration that inducs swelling).

The reason you have to "cook" things by heating them is to
1. Increase the rate of an exothermic reaction (which, like I said above, are likely very few, since these would occur spontaneously given sufficient time at room temperature),
2. Supply the energy necessary to sustain endothermic reaction,
3. Supply the energy necessary to induce phase change, and/or
4. Increase various transport properties, such as the diffusivity of water in pasta.

I designed an automatic pasta machine for a class project a few years back. Still looking for startup funds if anyone is interested in making a few mill.

edit:
To more directly address the OP, I suppose the second list could be changed to include
5. Change the selectivity of the endothermic reaction.

Toasting is essentially the controlled release of non-carbon atoms from the bread, which is likely an endothermic decomposition reaction. Burning toast is essentially taking the reaction to completion, so controlling the time and/or temperature in the toaster controls the extent of reaction.