Keeping objects destroyed during runtime of the game

Hello! I'm developing a game right now with diffrent scenes. The player starts in the Hub and changes to diffrent levels and always back to hub. I want the player to collect objects and keep them in the inventory. Im using this script:

 void OnTriggerEnter(Collider col) {
     InventoryHolder holder = col.GetComponent<InventoryHolder> ();
         if (holder != null)
     {
         ItemStack addItemStack = new ItemStack(item, amount);
         addItemStack = holder.AddStack(addItemStack);

         if (addItemStack == null)
             Destroy (this.gameObject);
         else {
             amount = addItemStack.itemCount;
         }
     }
 }

}

But if the Player enters another scene the inventory is empty again and when I return to the first scene all the objects are there again an could be collected a second time. How could I prevent this? I want the objects to be destroyed during the whole runtime of the game. Many thanks in advance!!