Item Transform - Unresolved

I checked related and none of the pages related to mine. Anyways, I am making a revamped food system, and after a certain amount of time, the food spoils (Ive already figured out how to make a timer). Im using an item instead of food because items are more versatile. After the timer expires, I want to remove 1 of the provided itemstack, and also add the spoiled version to the inventory. The problem is that you cant specify what player or mob contains the food in their inventory. I want all the procedures to be within the item, so the variables have to be entity (the item), x y z, and provided itemstack