That "wet hay" smell comes from old egg white, or some pasteurized brands. I use fresh eggs instead of pasteurized, but separating them into a blender bottle (like for protein shakes, with a ball whisk) and adding a barspoon of cold water for every four whites, shaking the Dickens out of it, and letting it rest a few hours in the fridge, gets rid of the smell. Also works for pasteurized, just have to do it in advance. I do use tap water for this, and I haven't ruled out that the chlorine may be what's fixing the smell. It's due to oxides forming and chlorine may 'unoxidize' some things.