I often buy fresh prepared masa from Mexican markets in order to make tamales and pupusas. Mexican cookbook authors stress getting the correct masa for the recipe, either masa for tamales or masa for tortillas. However, the masa at the market is in an unlabelled bag and is identified by the proprietor as just "masa". Questions:
is this more likely to be tamale or tortilla masa?
is there a real difference? What?
if there's a real difference, is there a way you can modify one type of masa into the other?
Clarifying: the above question is about fresh corn masa, not dried flour. Prepared masa, in particular, has at least oil and salt added to the fresh-ground corn.