Can mashed bananas be bagged and then frozen? Our family goes in spirts in the banana department.  It seems the only time they want them is when there isn't any, leaving the ones in the fruit bowl very lonely.  Can they be mashed into recipe portions and then stored in the freezer in freezer bags? I know they will turn black and need to reduce the extra liquid, but will the quality suffer?  I know you can freeze them whole, but freezer bags take up less freezer space.
It depends on the recipe.  Freezing and thawing bananas will result in a softer banana purée, significant separation of liquid, and browning. The longer they are in the freezer, the more pronounced each of these effects. For some uses (smoothies, banana bread), they should be fine for up to a few months, though the color will be affected if you care about that. You may want to just break them up into chunks rather than puréeing them before freezing, as chunks are much easier to separate than a big block of frozen purée, and much easier to portion out than full (peeled, of,course) bananas.