Can stale walnuts be rejuvenated?

If they’re rancid, then no. That means that the fat in the nut/grain/etc. has gone bad. Often if you buy from bulk bins at grocery stores, the stuff in there will already be rancid, or well on its way. You have to give everything the sniff test before you buy it.

Keep your excess walnuts in the freezer! That’s what I do. They stay good for much longer, and there’s pretty much no de-frosting time needed when you want to cook with them.

The oil is probably starting to become rancid. So you probably can’t do anything. You can try gently warming them in a pan on low to medium heat until they start to smell (that is toasting them).

Thank you very much. Store in the freezer from now on and I’ll try the toasting.

We buy big sealed bags at Costco and put about 2 cups of nuts in a lidded glass jar in the pantry (we eat a lot of nuts at our house) and keep the rest sealed tightly in the original bag, and then put inside a freezer zip lock bag in the freezer until we need to refill the pantry jar.

On a side note, if you like to use flax seeds, you should also keep those in the fridge or the freezer for the same reason, to avoid having them go rancid before you can use them. I also do the same for wheatberries.

@Kardamom: Yep, you can do the same with flour or any grain. I think that whole grains go rancid more quickly.

I toasted them in the oven for 20 min at 325 degrees. Still not good. Then I repeated the toasting process after coating them with PAM and sprinkling them with cinnamon sugar. MUCH better. I have a new big bag and will freeze them in 4 batches, as suggested.
Thanks all.