"such as outdated milk that is thrown out"

For something with a short life, there is no reason to track this purchase as Inventory. The products such as milk and fresh produce that spoil quickly if not sold, or are sold soon, they might as well be posted as Purchases of COGS and not held as inventory at all.

You might as well make it easier on yourself and not track things as Asset on hand, when that will require micromanagement from you.

Asset value is meant for the value of stuff "on hand over time" so that the Sale is not a long time period after the entry as expense. For milk and other "quick turnaround" products, just post them to COGS directly.