What is the relationship between cloudiness and coagulation in proteins?

[Megaevelie]

Coagulation of Proteins -- please help

We have a report tomorrow about this and I am not so sure of my results: (coagulation by heat)

Milk - no cloudy appearance, soluble in water
Egg white - with cloudy appearance, insoluble in water
Flour - no cloudy appearance, slightly soluble

I have researched for the confirmation of our results and only the egg white result is what I found to be sure of.

I do not know what's the connection of cloudiness to coagulation. Does it mean that new compound was formed?

Are all denatured proteins insoluble with water?

 

[nobahar]

Hi,
I don't know if this will be of much use to you, but until someone else verifies/corrects/expands, hopefully this will be of some help:
When you heat and denature a protein, it exposes hydrophobic regions that were previously concealed on the inside (for the most part) of the protein; all these exposed hydrophobic regions on different proteins are now forced together in the presence of water. This is what causes the coagulation.
I am guessing the reason it is cloudy is because all the proteins are coming together and so there is a lot of variation between different 'areas' of the solution in terms of protein concentration: if the proteins coagulate, they'll 'bunch together'; I can't think of a good analogy, but if you take it to the extreme, and they are all grouped together, then you'd just have a lump of all the protein molecules. Now imagine breaking this up, so that you get 'patches' of coagulated proteins in the water, if you keep going, then it will become 'cloudy', whereas a protein that did not coagulate at all would be distributed pretty much evenly throughout the water and so the solution would have a uniform colour (i.e. it wouldn't be cloudy).

 

[Ygggdrasil]

When interpreting the results, its worth considering whether the main component of each of these substances is a fat (lipid), protein, or carbohydrate, and which of these substances would be expected to be denatured by heat.