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I found in a book from 1500's that says that when you cook an egg (I assume a raw egg), it will get softer before it gets harder. Is that accepted by the science community today? Can someone explain to me how this is?

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  • $\begingroup$ Why is it closed? What exactly needs more details? What is not clear? $\endgroup$
    – user382541
    Nov 8, 2023 at 20:47
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    $\begingroup$ The question was closed for lack of details/clarity. For example, what do you mean by "get softer"? (Chemomechanics gave an answer regarding viscosity, but is that what you mean, and how are we supposed to know that?) As another example, what do you mean by "accepted by the science community"? (And how are we supposed to determine that? Poll every scientist in the world? Or do you just mean to ask if this is a valid egg fact or not?) Finally, the question is basically asking "what happens when you cook an egg"? Which is pretty vague. Lots of different things happen. $\endgroup$
    – hft
    Nov 13, 2023 at 19:30
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    $\begingroup$ @user382541 I suggesting rephrasing the question something like this: "In [include detailed reference information here], I found a claim that when cooking a raw egg (via such and such method described in the reference) that the egg gets software before it gets harder. Is this claim correct? If so, can you please provide more details about the physics of this cooking method?" $\endgroup$
    – Jagerber48
    Nov 14, 2023 at 7:59

2 Answers 2

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The white of an egg is a complicated mix of water and proteins. The viscosity of such a mixture as a function of temperature is almost impossible to predict but in general it will go down as the temperature goes up.

HOWEVER!!! As the temperature goes up, eventually you will hit the temperature point where the protein/water mixture will coagulate into a semisolid protein/water gel that we call a cooked white. As this chemical reaction proceeds, the viscosity of the material shoots up and it stops being a liquid altogether.

Therefore it seems reasonable to assert the truth of the book citation that you mention- but ideally, you'd need to perform an experiment to test that assertion. I encourage you to have this fun as soon as possible and report back with the results!

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    $\begingroup$ How would one perform such an experiment? $\endgroup$
    – user382541
    Nov 8, 2023 at 1:21
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The viscosity of homogenized liquid egg is reported in, for example, Bozkurt and Icier's "The change of apparent viscosity of liquid whole egg during Ohmic and conventional heating," J Food Process Engineering (2011).

The viscosity did indeed decrease from about 0.0085 Pa–s at 20°C to about 0.0069 Pa–s at 50°C before increasing again to around 0.0132 Pa–s at 60°C. This is consistent with the book's information (please give the citation to the book for completeness). We can attribute this nonmonotonic behavior to improved kinetics with heating, up to the beginning of protein crosslinking at around 60°C. Is this the kind of answer you're looking for?

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    $\begingroup$ The book I saw it in, is in Hebrew written by Rabbi Moshe Kazis (who was born in 1550), discussing Talmudical law (regarding the laws of cooking on the Sabbath) $\endgroup$
    – user382541
    Nov 8, 2023 at 1:26

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