I remember learning in Grade 10 Science class that an item can go through a chemical change, or a state change. A chemical change is irreversible. A state change can be reversed.
For example, if you have just purchased some ground beef and have brought it home, you might put it into the freezer where it will undergo a state change. It will freeze. When it is time to make meat spagetti sauce, the ground beef comes out of the freezer and into the fridge to thaw. State change again. Then the ground beef goes into the hot frying pan. Aha! Chemical change that cannot be undone.
It was either my science teacher or Bill Nye the Science Guy that taught me that. I took arts in university, so forgive me if my memory has failed.
They’re mostly carbohydrates, and all that’s involved with cooking them is htdration. Dry rice back out, and you’ve got minute rice. The denaturation that occurs when proteins (eg eggs, meat, cheese) are cooked is not readily reversible.
As far as the reversibility of cooked proteins goes, this example might help clarify the situation:
Take several hundred skeins of yarn, and place them in a box.
Sprinkle the yarn liberally with catnip, add a cat, and nail a lid on the box.
Shake the box intermittently for several hours.
Open the lid, CAREFULLY, there’s a mad cat inside !
Once you’ve made peace with the cat, examine the skeins of yarn, and attempt to restore them to their original, neatly ordered state.
It won’t be easy.
As I recall, in frying an egg, when the white hardens it’s coagulation, which is potentially (but not easily) revervsible in some cases. When the white is burnt into that cellophane-like stuff, it’s denaturization, which is not reversible.
First of all, it looks like I had it backwards–first comes denaturization, then coagulation. (I’m sorry, I’m going from a somewhat hazy memory of 30 years ago.) Perhaps what I was taught is not that denaturization is reversible in a practical sense, but that the protein is still identifiable. Coagulation is a more profound change, which is irreversible. I mainly wanted to contribute the fact in cooking proteins, there are different levels of change.
Simple protein denaturation is reversible, but it requires using chaotropic agents like urea (7M concentraion) or guanidine hydrochloride. These chemicals are bad juju in working concentrations. Then you have to very carefully remove the chaotropic agent and replace it with a more friendly solution. It is very tricky, fiddly, cussed danged rotten late-night, great googly moogly it’s already midnight my wife is gonna kill me for not coming home, kind of work. I do not recommend trying it.
“Coagulation” is a possible effect of denaturation.
Now, after denaturation comes hydrolysis, wherein the protein’s backbone is actually broken. This can be done with acid, heat, ionizing radiation, enzymes, or even a great deal of agitation (with ultrasonics). Theoretically, even this can be restored with the right enzymes and raw materials.
The most practical way to restore a grilled steak to being raw beef would be to grind it up and feed it to a cow, and you’d still lose some of it.