Can Worm Castings Go Bad?

I bought a fairly large bag of worm castings last year and hardly used any. They have been stored indoors, inside of the bag that they came in, the bag has been open the whole time. Looking inside of the bag a section of the castings seems to be turning white. Kind of like old dog poop used to look back in the day.
I'm guessing this is just part of the natural break down process, but can this be harmful to plants? or throw off PH or anything like that? Basically I want to know if these worm castings are still usable or if I need to throw them out.

So old dog poop looks different now? Weird. The pH will change over time as bacteria and fungal species break things down, but it should still be OK to use if it doesn't smell bad. Personally, I would probably just use it outdoors and buy new, but I doubt it will cause harm. The white that you're seeing is most likely a beneficial fungus. If you have an enzyme product you could irrigate the castings with that several days prior to mixing your soil, that would also help break down any undesirables.

Thanks, Wolverine. I think I will mix them in with some random plants first to make sure there are no problems.