I learned from some of my retail/service jobs that ketchup doesn't need to be refrigerated. Opened and partially used containers of tomato sauce/paste does, but the extra sugar in ketchup combined with the acidity of tomato sauce keeps it unspoiled for a long time. I use enough of it that the larger containers never go bad/contain mold by the time I'm finished with them, but un-sweetened tomato sauce has to be used within a shorter time or else mold will grow.