You’d need to administer it in such a way that you can’t detect it by taste, and as pmoriarty says, to be double blind is a further challenge. You can however modify your protocol. Instead of chocolate buy some unfilled pill capsules (very cheap) and have a friend fill half with a pinch of salt, and half with a pinch of MSG. This friend makes a note of which caps are MSG, and without informing you or your SO which is which. The friend can simply assign each cap a day, and keep the key to which day is MSG in a notebook and be revealed later. From there, follow your protocol. It’s now double-blind, and you won’t taste what it is you’re taking and have some subconscious reaction.
I intended to write that s/he should just swallow the chocolate to not taste what's inside but I forgot. I mean if we are gonna give this dude headaches at the least let's make it chocolate?
