This is a common question on Google.

E621 is derived from plants, so it should be fine.

Technically, no. but click this and then you can have e621 halal.

It's a misconception that the categories "halal" and "haram" in Islam are only concerned with food. In fact, they are used to describe permitted and forbidden things in general. Suffice it to say that in most orthodox schools of Islamic jurisprudence, e621 would be haram (forbidden). Your more liberal strains of Islam might be okay with it, but they'd have to be pretty liberal indeed.

kora_viridian said:
https://i.kym-cdn.com/photos/images/original/001/126/018/ed6.jpg

Seriously, it seems to depend on how the E621 was made. If it was made without involving pork, then it's halal. If pork was involved, it's haraam. If the method is not known, it's mushbooh, which means "suspicious", and I think means "probably not halal".

Related question: is E621 kosher or treif?

Ac’cent, which is pure E621, says it's kosher, and has an OU mark. I'm not sure if it's kosher for Passover, though.

Disclaimer: I'm not Muslim or Jewish.

To be kosher for Passover, something cannot be made with chametz (certain grains) or, for Ashkenazi Jews, kitniyot (certain other grains and legumes). Monosodium glutamate is usually produced by bacterial fermentation of a broth that may well include these ingredients, but some poskim (deciders of Jewish law) have ruled that the fermentation process is sufficiently transformative that the resulting product is nevertheless kosher for Passover.