Speaker 1: Welcome to Brainstuff from house stuff works dot com where
Speaker 1: smart happens. I am Marshal Brain with today's question, why
Speaker 1: do eggs turn hard when you boil them? Eggs are
Speaker 1: rich in protein, especially the egg whites. It's this protein
Speaker 1: that causes eggs to become hard when you boil them.
Speaker 1: Here's how it works. Protein is a chain of amino acids.
Speaker 1: These amino acid strings fold back of themselves, and the
Speaker 1: way the strings fold determines the proteins chemical and biological properties.
Speaker 1: The proteins are held in place by weak bonds, that is,
Speaker 1: non covalent bonds between different parts of the amino acid string.
Speaker 1: When you break those strings by various methods, you are
Speaker 1: doing what's called denaturing the protein. You can do nature
Speaker 1: a proteinen in several different ways. Here are two ways
Speaker 1: to do it with eggs. The first is heat. When
Speaker 1: you heat an egg, the proteins gain energy and literally
Speaker 1: shake apart the bonds between the parts of the amino
Speaker 1: acid strings, causing the proteins to unfold. As the temperature increases,
Speaker 1: the proteins gain enough energy to form new, stronger bonds,
Speaker 1: in this case covalent bonds with other protein molecules. When
Speaker 1: you boil an egg, the heat first breaks or unfolds
Speaker 1: the proteins and then allows the proteins to link back
Speaker 1: together with other proteins, so the egg white turns from
Speaker 1: this kind of liquid e mass into something that's much
Speaker 1: more like plastic. The second way to do nature proteins
Speaker 1: is to use chemicals. You can break the weak bonds
Speaker 1: between protein molecules with chemicals, and then they can link
Speaker 1: back together in the same way. Heat causes this to happen.
Speaker 1: According to an experiment done by the bat BC Science Shack,
Speaker 1: if you put vodka on an egg white, the alcohol
Speaker 1: in it breaks weak hydrogen bonds in the protein. If
Speaker 1: you put vinegar on an egg white, the acid in
Speaker 1: it breaks ionic bonds. If you mix the two, the
Speaker 1: vodka and the vinegar together, you break both types of
Speaker 1: bonds and quite effectively de nature the protein. You do
Speaker 1: something similar when you whisk egg whites. By exerting mechanical
Speaker 1: energy in the whisking process, you cause the protein bonds
Speaker 1: to break and subsequently to reconnect. Once these new strong
Speaker 1: bonds are formed, the eggs stays in that state. The
Speaker 1: proteins have formed a network of strong, permanent cross links.
Speaker 1: A cooked, chemically altered, or well beaten egg will never
Speaker 1: go back to its original state. When cooking eggs, use
Speaker 1: moderate heat. High heat causes the protein and eggs to
Speaker 1: become tough and rubbery. Be sure to check out our
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