Do you think industrial safety standards that companies spend tonnes of money on maintaining every year just popped out of thin air or the good will of companies?

Hell no. The mega-corps at least would be chucking children into factory machines 7 days a week like back in to early 20th century if they thought they could get away with it.

If you want companies to do something they're otherwise not incentivised to do, you regulate it into existence. Force their hands just like Governments did in the past, and have now become increasingly less willing to do because of blatant corruption.

The easiest path in my mind is a one-two combo...

Firstly you give minimal liability to the food donor, so as long as they made a good faith effort to check the food wasn't bad before handing it over you can't be sued (I.e. if you're giving a batch of cans, you'd check them for defects like bloating or cracks/dents).

Secondly, you create criminal liability for throwing away non-defective shelf stable foods (such as dried, canned and/or jarred foods) for companies over a certain size (to prevent from screwing over small businesses that may not have the logistics to ensure consistent donations).

Those two things create a pathway by which donations can be made with minimal risk, and disincentivise the route of least resistance (aka. Throwing it all away).