What happens at a molecular level to soften food when it cooks? Why do things become harder when charred?

Submitted by Singhilarity t3_z5svr1 in askscience

What is going on? A piece of raw meat is moderately firm, if supple. Cooked well, it becomes phenomenally soft tender and soft, such that it barely requires chewing; HOWEVER, with the heat applloed differently, it can char into an even firmer, harder, state.

What's going on chemically? Obviously the intensity and time of the heat applied plays a role; what other factors are involved? Are there consistent principles? What are they?

Thanks much!

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Soft_Injury t1_ixz12y5 wrote

The first part is due to denaturing of the proteins in the meat. Proteins present in the meat in the absence of heat exist in their natural conformation, where interactions between amino acid residues keep proteins in this shape/conformation. In the presence of heat these interactions are overcome by heat energy and the proteins are unfolded/denatured and this is part of why meat will become more tender.

The char part is due to excessive heat which will reduce the carbon compounds on the surface of the meat, resulting in a variety of hydrocarbons that have different physical properties.

That is the gist of it, I’m sure I am leaving some things out, but hopefully this will help your understanding somewhat.

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kingcat34 t1_ixz1y5u wrote

Just to add to this good answer, that obviously the longer you cook something the drier it will become too, which adds to the hardening of food without the charcoal

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bbbbaconsizzle t1_ixza72s wrote

Why, when cooked poorly, even though heated, gets tough and chewy. Even though drying or charring or cut of meat may not be a factor.

One instance I specifically recall is a wrapped roast made years ago and ran out of propane part way. Not sure how long it had cooled before moving it to the indoor oven. Toughest roast ever. Like chewing tires. Inedible despite good flavor. Even in tiny little pieces. Always wondered why that was, scientifically. Wasnt the cut or animal. Others in that beef were very tender.

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redligand t1_ixzcfo3 wrote

Cuts of meat that requires long, slow cooking usually have a lot of connective tissue which takes longer to soften than muscle tissue. The large structural proteins like collagen in connective tissue are more stable and heat resistant.

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bbbbaconsizzle t1_ixzfmpy wrote

Of course, but that gap in cooking time completely broke the process. We did everything to try and save it. (it was large and meat expensive) it went through more time slow cooking to no avail, after that different chunks went through different processes, even more time slow cooking, cubing and stewing, grinding it up for taco but the rubber pellets were not overly palatable, I can't recall what else.

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Candelestine t1_ixzt618 wrote

I'd put forward the hypothesis that maybe some of the fats had time to polymerize? Once that process is done, you're not going to be able to undo it by cooking.

Normally a lot of the fat will render out and get discarded. But if enough was still present and had enough time, or maybe the presence of a catalyst, maybe that could explain it?

Would be my first guess anyway.

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Indemnity4 t1_iy1697q wrote

Your process is an old trick to make meat dishes like ribs.

Usually you want to slow cook so that the meat reaches an internal temperature of 70°C. The tough, chewy collagen tissue is broken into smaller gelatin molecules that melt, baste the meat and taste delicious. It's that shiny gooey liquid in the bottom of the dish. This is the internal temperature to achieve falling apart tenderness of slow cooking.

At lower temperature of 60°C the tough, chewy collagen tissue starts to denature without melting. It is almost like cooking egg white - the protein is changing but it's not breaking. As a consequence, the meat can shrink by 20% in size and it becomes very chewy. Leave it at 60°C too long and it squeezes out all of the moisture from the meat and gets really hard.

You cannot recover from partially cooked meat. Not unless you do other tricks such as marinating with vinegar, or pounding it with a hammer. or essentially steaming it to get moisture back inside.

The trick for the ribs is cook them until falling apart tender, then put them in the fridge overnight. The gelatin will set really hard. Next day, you heat up the ribs just enough to denature the gelatin, and you have falling-apart-delicious-tender meat, but the gelatin has denatured and set hard, so the meat stays together for serving without being disintegrating at first bite.

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