Yes, it does and it is quite easy to tell how.
After my trip from America, I returned to my apartment to find my kimchi covered in a thick coat of white mold. I think I should have expected it because the container was very big and only half filled with kimchi. Also, I had not completely submerged the cabbage with the red kimchi juice.
This was devastating because my mother had made the kimchi by hand and shipped it to me.
I thought all was lost until I told my coworker Yejung about it. She told me that if I carefully removed the moldy layer- making sure not to get any mold spores on the rest of the cabbage and moved it into a fresh container all should be ok. She said the kimchi below that might have even improved.
When I went home, I did as suggested. I smelled the remaining kimchi and it smelled like...kimchi. I tasted it and it also tasted right- actually a bit better (this kimchi would be good for fried rice and stews).
I moved the kimchi into a glass container with plenty of juice. I saved quite a bit of my mother's kimchi.
So what I learned is that:
1. Kimchi can go bad.
2. Kimchi should be stored in a container that had a good seal and with not too much air.
3. The vegetables and leaves should be submerged in the juice. If there is not enough juice add a bit of water and mix it around.
4. Kimchi with mold can be saved. The moldy parts need to be carefully removed and not mixed in with the rest of the kimchi.
5. You should check the remaining kimchi by smelling it. If it smells moldy, throw it away.