I understand that we want to have a consistent data structure for representing Ingredients, but I can't envision a use case where a system would have actual Ingredient instances.  I just don't see the case for re-use of Ingredients across products.  It might seem similar to Medication but where that differs is that we have systems that are maintaining recipes of compounds and referring to them with Medication instances.   I just don't see systems communicating the "100mg acetaminophen active ingredient" in the same manner.  I certainly don't see business identifiers for ingredients.