also curious if anyone knows what temperature matlodextrin breaks down at, if any.
Hm, that's a tough one. It sounds like the folks from Modernist Cuisine might be a great resource for this. Can you explain a bit more about what you're doing with it?
there are two types of activa, rm and ym. one specifically for meat, the other for dairy. I do not want it to react with the butter, but only the meat.
Activa will only bind to your proteins, so it shouldn't react with butter at in all a recipe. I would imagine, though, that (depending on when your butter is added), too much would prevent activa from working as well as it could.
The Modernist Cuisine Team says, "Activa won’t react with butter. As for maltodextrin, do you mean breakdown or dissolve? Which type of maltodextrin are you using?"