Scoop the minnows into a ziploc bag, pour rubbing alcohol (or cheap vodka), seal them up for 15 minutes. Drain all the alcohol out, then reseal and freeze them. Mine are never mushy, in fact almost leathery, but still have the same potency on the perch. I often cut them in half and still the perch will take them.

I do not see a noticeable difference between live and frozen with the way I freeze them. I've run out of live and started using frozen with no change in bite frequency. When the perch bite is on, it's on!