I thought this was fixed but looks like not. It's can either be annoying or exploitative if you play as a cannibal pawn.
Farm nutrient paste meals using common ingredients, then place human meat and farm just 1 nutrient paste meal and then merge all nutrient paste meals. Now all nutrient paste meals contains human meat as ingredient.
Is it possible prevent stacking meals that uses specific ingredients?
Old things since we got human meat.
No there is currently no way to split meal by components.
I suggest that you let a pawn cook cannibal food.
The CommonSense mod adds a Comp that fixes that.