how to record loss of product value?

Thanks for coming here with us today, ConA.

You'll want to consult an accounting professional to help you decide which accounts to use in your Journal Entry. 

Here's how to create a Journal Entry:

1. Go to the Accountant menu.
2. Choose Make General Journal Entries.
3. Click Save & Close.

Here's a good reference to learn more about creating a journal entry in QuickBooks Desktop.

If you wish to review the entries, you can do so by going to the bottom pane of the Make General Journal Entries window.

By default, only entries from the last month are displayed. To change or expand the list of entries, click from the List of Selected General Journal Entries drop-down list and select which period.

If there's anything else you need help with, just let me know. I'm always happy to assist. Stay safe and have a great rest

@ConA 

There is no adjustment to be made at this point.  You should keep the value at the original cost.  If you lower the value of inventory, you would be creating an expense that cannot be measured and the IRS doesn't like that.     

Thank you so much for your reply. So, all I can do to donate or to sell very low, that will be way below the cost, and the books show a loss this way, correct?

@ConA 

You got it.  Whether you donate it (sell it for $0) or sell it below cost, the average cost of that item will get booked to COGS as of the sale date.

Thank you so much! Makes sense.