WEBVTT - Why do eggs turn hard when you boil them?

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<v Speaker 1>Welcome to Brainstuff from house stuff works dot com where

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<v Speaker 1>smart happens. I am Marshal Brain with today's question, why

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<v Speaker 1>do eggs turn hard when you boil them? Eggs are

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<v Speaker 1>rich in protein, especially the egg whites. It's this protein

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<v Speaker 1>that causes eggs to become hard when you boil them.

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<v Speaker 1>Here's how it works. Protein is a chain of amino acids.

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<v Speaker 1>These amino acid strings fold back of themselves, and the

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<v Speaker 1>way the strings fold determines the proteins chemical and biological properties.

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<v Speaker 1>The proteins are held in place by weak bonds, that is,

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<v Speaker 1>non covalent bonds between different parts of the amino acid string.

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<v Speaker 1>When you break those strings by various methods, you are

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<v Speaker 1>doing what's called denaturing the protein. You can do nature

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<v Speaker 1>a proteinen in several different ways. Here are two ways

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<v Speaker 1>to do it with eggs. The first is heat. When

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<v Speaker 1>you heat an egg, the proteins gain energy and literally

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<v Speaker 1>shake apart the bonds between the parts of the amino

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<v Speaker 1>acid strings, causing the proteins to unfold. As the temperature increases,

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<v Speaker 1>the proteins gain enough energy to form new, stronger bonds,

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<v Speaker 1>in this case covalent bonds with other protein molecules. When

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<v Speaker 1>you boil an egg, the heat first breaks or unfolds

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<v Speaker 1>the proteins and then allows the proteins to link back

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<v Speaker 1>together with other proteins, so the egg white turns from

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<v Speaker 1>this kind of liquid e mass into something that's much

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<v Speaker 1>more like plastic. The second way to do nature proteins

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<v Speaker 1>is to use chemicals. You can break the weak bonds

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<v Speaker 1>between protein molecules with chemicals, and then they can link

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<v Speaker 1>back together in the same way. Heat causes this to happen.

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<v Speaker 1>According to an experiment done by the bat BC Science Shack,

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<v Speaker 1>if you put vodka on an egg white, the alcohol

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<v Speaker 1>in it breaks weak hydrogen bonds in the protein. If

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<v Speaker 1>you put vinegar on an egg white, the acid in

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<v Speaker 1>it breaks ionic bonds. If you mix the two, the

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<v Speaker 1>vodka and the vinegar together, you break both types of

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<v Speaker 1>bonds and quite effectively de nature the protein. You do

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<v Speaker 1>something similar when you whisk egg whites. By exerting mechanical

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<v Speaker 1>energy in the whisking process, you cause the protein bonds

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<v Speaker 1>to break and subsequently to reconnect. Once these new strong

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<v Speaker 1>bonds are formed, the eggs stays in that state. The

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<v Speaker 1>proteins have formed a network of strong, permanent cross links.

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<v Speaker 1>A cooked, chemically altered, or well beaten egg will never

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<v Speaker 1>go back to its original state. When cooking eggs, use

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<v Speaker 1>moderate heat. High heat causes the protein and eggs to

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<v Speaker 1>become tough and rubbery. Be sure to check out our

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