Well I've been researching and it looks like you were right about most commercial butter flavours containing Diacetyl, i have found this : Imitation Butter Flavor which is said to be maid of : a mixture of water, propylene glycol, artificial flavor, and FD&C yellow 5. If I added this at secondary would it negatively affect my brew? What about well I'm boiling my wort? Thanks for the insight.