Citric acid for hard-boiled eggs? I recently ordered some dish from a local food delivery company. The dish, among other ingredients, contained hard-boiled eggs. The ingredient list read the following:


  [...] Hard-boiled eggs (egg, citric acid), [...]


Due to that formatting, the citric acid was definitely used for the eggs, not for the dish as a whole. I am wondering what the purpose of using citric acid for cooking hard boiled eggs could be. I am not sure how/in what quantity/when it is added to the eggs. I could think of a few possible reasons to using it, however, I am not sure if any of these is real. My ideas are:


Perhaps, given that it is acid, it helps removing the bacteria and/or feces remnants from the shell, or
Given the lime content of egg shells and the fact that lime is pretty reactive to some acids, it might help with peeling. It sounds reasonable as we are talking about a food delivery company, probably cooking eggs up in the quantities of the hundreds to thousands.


These are just my two cents, does anyone know the (possibly) real reason behind it?
US patent EP0020011 A2 describes a process of packaging shelled hard boiled eggs where the egg is dipped in a citric acid solution to prevent discoloration of the yolk at the white-yolk interface. I would guess that’s what is going on in this case.