I made homemade tamales for the first time yesterday and I think they turned out well, but I had a question about the masa I used. I bought a bag of masa sin preparar and it sat on my counter for 5 days before I used it. The sell-by date was the same date that I made the tamales, so I assumed it would be okay, but it did smell a little funny. I'm wondering if I should have kept it in the refrigerator or if it's okay to leave out on the counter. It wasn't refrigerated at the store.
Yes, masa can be refrigerated. Most Mexican tortillarias in my area do not sell it refrigerated because they know it's going to get used pretty quickly. At least one of the Mexican market here sell both refrigerated and unrefrigerated masa.
I almost always refrigerate my masa when I get it home and then allow it to come back up to room temp before I use it. Masa does tend to ferment if not used within a couple of days.