Why do we add vinegar when we are poaching an egg?

Dr Robert Keyzers, from Te Wānanga Matū—School of Chemical and Physical Sciences answers:

"On the inside of your standard chicken egg we have two main components. We have the egg yolk and then we have the egg white.

"The egg white itself is comprised of a bit of water and mostly a protein called ovalbumin.  When you start to heat up a protein like ovalbumin something called denaturation starts to occur and that’s when the protein breaks down and it starts to solidify. But we can also do denaturing in other ways. The other way is to increase the acidity of how you’re cooking it.

"Vinegar is an inherently acidic material, so if we add a few drops of vinegar into that boiling water that is going to increase the rate of denaturing and it’s going to make that happen faster and help the poached egg hold its shape better."