Heat and Protein

A_Sober_Paddy

Hey all,

I'm just looking for some help with an explanation of what happens to protein when heated...I know it becomes denatured but affect does this actually have...

I'm just wondering whats the difference between denatured protein and regular protein in terms of the benefits it has to the body...

If you could answer in laymen terms it would be greatly appreciated:)

Woodward

Generally denaturing a protein will destroy its function. Proteins ability to do its job depends on its conformation and denaturing it destroys this

SOL

what woodward says is right, basically it works like this:

Proteins are made from ~ 21 different types of amino acids, but each protein can be hundreds or thousands of amino acids long.

When a protein is made inside a living thing it is made with a specific shape, the different functionalities on each amino acid point in a certain way and give it a certain shape that allows it to have a function.

Ultimately, what allows it to hold this shape is the environment around it, while the bonds that hold each amino acid to the next one are super strong and very hard to break, the bonds that hold it in shape are not. If you change the environment of a protein it will change its shape and that is basically what denaturation is.

If you heat the protein up too much (like frying an egg), the shape of the proteins becomes disrupted and changes into random shapes.
There are lots of other ways to do this too like putting a protein in really salty water or in an organic solvent or treating it with certain chemicals.



What this means for a person eating it is interesting. Being able to denature proteins is very important as it allows us to kill germs that would otherwise make us sick. It also can make the protein more digestible, but ultimately, as far as I understand, besides the hygiene advantage it does very little to the nutritional value of the food because your body still breaks down the proteins for use anyway. (also, your stomach is a pretty good place for denaturing proteins).

A_Sober_Paddy

So from a nutritional standpoint, if you denature whey protein it will still provide the same amount of protein as if it wasn't denatured?

Lbeard

SOL wrote: »

What this means for a person eating it is interesting. Being able to denature proteins is very important as it allows us to kill germs that would otherwise make us sick. It also can make the protein more digestible, but ultimately, as far as I understand, besides the hygiene advantage it does very little to the nutritional value of the food because your body still breaks down the proteins for use anyway. (also, your stomach is a pretty good place for denaturing proteins).

Any idea how much energy is required to digest/denature raw meat over cooked meat?


Is the body particular about which form of protein it receives? Or does it just take the 21 amino acids from whatever it gets?

SOL

To be honest I'm not entirely clear on this...

For example, proteins which are harmful such as prions which cause CJD are apparently so stable that they are not denatured in cooking or digestion and result in death. Which leads me to suspect that the level of energy required to denature a given protein varies enormously.

In some manner the nature of the protein will dictate how easily the amino acids are metabolised too, since it has to be cut up by enzymes, and then split apart, and the manner of this is irrelevant to how much energy is going to be needed.

I suspect that there might be some literature about this, you could even ask in the biology forum and you might get someone who knows lots about this kind of thing. Alternatively, I would imagine that at some evidence could be gleaned from nutritional studies of various proteins although this raises the other problem.

That is, that as you point out all 21 amino acids are needed for protein synthesis by your body, but your body can only make some, therefore it requires the others to come from the diet. It is possible to eat sources of protein which don't contain these and you then wont be able to produce protein in your body.
This is a problem with vegetarianism because plant proteins don't usually have all the required amino acids and therefore without careful selection of diet malnutrition can occur.

Lbeard

SOL wrote: »

That is, that as you point out all 21 amino acids are needed for protein synthesis by your body, but your body can only make some, therefore it requires the others to come from the diet.

Find an animal that looks healthy and well nourished ...and then eat them.

This is a problem with vegetarianism because plant proteins don't usually have all the required amino acids and therefore without careful selection of diet malnutrition can occur.

Doing a quick check. It would seem that there is a difference in distribution of amino acids across different plants, but if you eat the different kinds you will get all the acids. A mixture of rice and corn, as the internets sez, should cover you. The Chinese and Indians are getting bigger, because they now have more diversity in their crops.

Nutrition info is always a bit patchy. "Five a day" is something pulled out of thin air. "Have you had all your 21 amino acids today?" could confuse people.

I have an interest in this at the moment, as I may need to stop eating meat and fat for health reasons. There are abnormal levels of triglycerides in my blood, which are not really explained by my diet. I may need to cut them out or down to the absolute minimum. I think the problem for vegetarians is not so much not being able to get the amino requirements, it's that the protein is harder to break down. And that you may need to get through an unhealthy level of carbs to get the protein. Russian health problems of the past, were in large part not due to gorging themselves on animal fats and proteins, but by eating largely vegetarian starchy diets.

I've been trying to look into non-meat based protein sources - or fat free protein extract. "Does this mixture contain all 21 amino acids" - in the whole diet business there is a lot of hokum and crap.

It is possible to eat sources of protein which don't contain these and you then wont be able to produce protein in your body.

In George Gamov's Inside Mr Thompkins. He has a story where Mr. Thompkins son, goes to south America and gets a shaman to take him through a 3-dimensional Mobius strip in the jungle. Okay. A Mobius strip is 2-d, but there's an interesting thing about it, in that if you were 2-d and you walked around the strip, and emerge after a single circuit, you will be upside and your left will be right. If a 3-d Mobius circuit existed then you would emerge your left being right.

Mr Thompkins son emerges for the Mobius circuit, and he is laterally inverted. But then he finds he can only digest fat and vodka. All the amino acids are in their left-handed enantiomer, while his body now needs the right.

SOL

You could take up eating rabbit, it contains so little fat (any is lacking some essential fatty acids) so it results in Rabbit Starvation if you don't eat other things aswell!

As for the amino acids lark, well, labelling in general on food is frustratingly vague in some ways, but I wont hold out hope...

Also, 5 a day was invented because 3 fruit and 3 veg a day was too complicated and people weren't sure what fit into which category...

Yay, people