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.

As the 'How to make says", simply "shake all ingredients" including the raspberries. There is no need to muddle them as shaking should be sufficient pulverise them. I've added a note in brackets for others who are flummoxed.