I made gochujang about a month ago and today there was mold on top. I talked to my local Korean grocery store ladies and they said to stir a little more salt into the gochujang and put a layer of salt on top, scraping it away when you need to take some out. I went ahead and did this, so I hope that helps. It looks great and tastes good too. Any other pointers to keep it fresh and safe to eat? I have it stored in a big onggi jar right now.