27

I've been taught 2 things that seem to contradict each other:

  • Cooked meat has plenty of protein
  • Heating proteins denatures them and damages/changes them

If this is the case, then cooked meat must have very little usable protein, which is clearly not the case.

How does protein in a fully cooked food, e.g. chicken/pork/eggs survive the cooking process in a usable form?

Note I'm not asking about burnt meat, browning or flavour reactions, or rare meat e.g. a medium/rare cooked steak.

Tom J Nowell
  • 399
  • 4
  • 7
  • Note this is my first Q here and I wasn't sure if this should go here or on a chemistry stack. If so happy for this to be migrated. ( also no protein tag?! ) – Tom J Nowell Jul 31 '22 at 18:37
  • 1
    I think this is a fair question and hopefully someone with the expertise can give a full answer. I expect that the issue of heat is no different to strong stomach acids which will also denature, change and break down the proteins – the digestive process is all about breaking food into constituent components which the body then uses. – dbmag9 Jul 31 '22 at 19:05
  • 6
    My judgement is that this is a "nutrition" question and therefore off-limits for this SE. That's also why there's no "protein" tag. – FuzzyChef Jul 31 '22 at 20:17
  • @FuzzyChef Indeed, it's really a question about digestion, so perhaps a better fit for Biology SE? – Jack Aidley Aug 01 '22 at 08:35
  • 1
    oh I don't give a hoots about digestion, it's the cooking process itself I'm interested in – Tom J Nowell Aug 01 '22 at 12:44
  • 2
    Think of it like recycling glass. The glass is smashed into pieces and rebuilt into a new bottle. – eps Aug 01 '22 at 15:00
  • 5
    Note that I am not asking for nutritional or medical advice, I have no interest in the dietary consequences of this and the nutritional value of cooked food is of no consequence to me. It's the act of cooking itself that I'm asking about – Tom J Nowell Aug 01 '22 at 15:49
  • Ever heard of prions? Those are proteins and cooking doesn't destroy them enough. – DKNguyen Aug 01 '22 at 16:42
  • 1
    "and damages/changes them", not necessarily. Further, many proteins are not taken wholesale from the foods you consume, but its actually the amino acids that are used. The proteins are broken up during digestion anyway. Among Vegan propaganda there are lesser claims that *raw* food is better for you. It's one of those real ironies, since virtually the opposite is true. Cooked food is almost always better for you and easier to digest. – 25939 Aug 01 '22 at 20:27
  • 1
    Denatured proteins are still proteins, just different proteins. Proteins have multiple structures, each important to their function. Primary, Secondary, Tertiary and even Quaternary structure. Changing any of those will damage their ability to function correctly. – Aron Aug 02 '22 at 07:14
  • 4
    Your stomach acids also denature any proteins that you ate raw... – Hobbamok Aug 02 '22 at 10:22
  • Cars have iron in them. Heating cars can damage and melt the iron in them. Melting the iron in a car does not reduce the amount of iron in them. – Aron Aug 04 '22 at 05:13

4 Answers4

61

Structural proteins in foods, i.e. albumin in eggs, myosin in muscle meats, gluten in wheat, are formed by amino acids in complex structures. Proteins are folded and clumped chains of peptides, and peptides are chains of amino acids. Your body uses stomach acid and proteases (enzymes) to break down proteins in digestion, but this requires time and energy (stomach churning, body heat).

The amino acids are what your body requires. They're used to build more complex proteins. Cooking gives a head start in un-clumping/unfolding proteins, and in some conditions into peptides and amino acids, that are easier for your body to digest making them more 'bioavailable'.

Some of these amino acids can be produced by your body using nitrogen compounds from breaking down other amino acids and nutrients. The ones your body can't produce on its own have to be obtained in the proteins you eat. These are called 'essential amino acids'.

Different protein sources have different amino acid compositions, giving them different 'protein values' in how complete the range of essential amino acids are available; i.e. collagen/gelatin is a common structural protein that provides great texture for sensory applications, but the protein value is 0 for regulatory labelling requirements in some countries since it is missing an essential amino acid.

borkymcfood
  • 5,370
  • 16
  • 34
  • 17
    This is why the discovery how how to make fire was such an important point in human development; cooking gave more nutrition from food, less hunting was needed, more time could be spent on other pursuits. – GdD Aug 01 '22 at 07:49
  • 19
    I'd move *The amino acids are what your body requires.* to the top or highlight, maybe even TL;DR. That is the essence of the answer. – manassehkatz-Moving 2 Codidact Aug 01 '22 at 15:08
  • 2
    @manassehkatz-Moving2Codidact exactly what I was going to reply. The reason denaturing protein isn’t bad is that we didn’t need that protein in the first place. – Sebastiaan van den Broek Aug 02 '22 at 03:43
  • At least collagen makes more collagen (which the body needs to make). – Joshua Aug 02 '22 at 16:02
  • 1
    Minor nitpick from a pedantic biologist: *"Proteins are folded and clumped chains of peptides, and peptides are chains of amino acids."*. That's not quite right. Peptides are simply pieces of protein chains. Proteins are made up of folded and clumped chains of amino acids, not of peptides. – terdon Aug 03 '22 at 15:52
29

The denaturing of proteins refers to their physical structure, not their nutritional value. This might help. As is detailed in the link, heat, acid, salt, alcohol, and mechanical agitation can cause proteins to denature. This denaturing is when the folded strands of protein unfurl into a long strand of amino acids.

moscafj
  • 72,382
  • 3
  • 117
  • 207
7

Another way to think about proteins and tissue is like lego blocks. Imagine the tissue or steak you eat is a well-crafted lego structure, for example a building. Heating it might break apart some of the corridors, or remove a floor from the other floor but the individual lego pieces are still mostly intact. What your body needs from the protein you eat are individual amino acids, legos in this case. Your body must still further break down the corridors/building floors (steak) into individual legos (amino acids) which your body can absorb in your small/large intestine.

In this case, cooking might slightly break down your building (steak) but it won't break it down all the way to the level of individual legos (amino acids) which your body needs.

Biologist
  • 71
  • 1
0

Another analogy would be, if you smash up a car engine so it cannot run anymore, the engine is 'destroyed' yet you still have all the scrap metal. And as our body wants protein in the smallest possible scraps (amino acids) cooking, denaturing, smashing up, is useful. Becuase proteins have complex strucures that enable them carry out their purpose, changes to the structure 'destroy' the protein, i.e. destroy their ability to carry out their purpose. Note that denatured alcohol is different. the structure of alcohol is too simple to destroy (unfold). Denatured alcohol cannot be used for it's main purpose (getting you nice and drunk) because something has been added that makes it undrinkable (like the hideous taste of some alcohol gels if you use them, then eat food then try to lick your fingers).

user100361
  • 1